diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7bdcb92..bc74e12 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -43,7 +43,7 @@ jobs:
       - name: Check installer
         run: |
           sudo apt-get update
-          sudo apt-get install -y shellcheck
+          sudo apt-get install -y shellcheck sqlite3
           bash -n install.sh tests/install_test.sh
           shellcheck -x install.sh tests/install_test.sh
           bash tests/install_test.sh
diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index b27a38c..691eb6e 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -30,7 +30,7 @@ jobs:
       - name: Check installer
         run: |
           sudo apt-get update
-          sudo apt-get install -y shellcheck
+          sudo apt-get install -y shellcheck sqlite3
           bash -n install.sh tests/install_test.sh
           shellcheck -x install.sh tests/install_test.sh
           bash tests/install_test.sh
diff --git a/README.md b/README.md
index b12d221..af8f0d7 100644
--- a/README.md
+++ b/README.md
@@ -37,13 +37,13 @@ bash <(curl -fsSL https://raw.githubusercontent.com/zxyszx/NewSzxcn-Email/main/i
 
 脚本会先显示统一管理菜单。空白服务器默认选择安装，并进入防火墙、邮件域名、管理员
 账号和 Web 部署方式的引导；检测到已有安装时默认选择安全更新。选择重新安装会先将
-`/opt/newszxcn-email` 完整改名备份，再进入首次安装流程。更新会先备份数据库，并在
-启动失败时自动回滚。
+`/opt/newszxcn-email` 完整改名备份，失败时自动恢复原目录、Nginx 和旧容器。更新前会
+校验数据库备份并保存镜像、Compose、环境、安装脚本和 Nginx，失败时执行完整恢复。
 
 脚本会自动完成：
 
 - 安装或检查 Docker Engine 与 Docker Compose v2
-- 首先选择仅开放必要端口、保留现有防火墙或开放全部端口
+- 选择自动添加邮局必要端口规则，或保留现有防火墙由用户自行配置
 - 询问邮件域名、管理员用户名和密码；默认用户名为 `admin`，回车自动生成 12 位密码，自定义密码最少 6 位
 - 选择自动 Nginx + SSL、宝塔/已有 Nginx 反代或 HTTP 测试模式
 - 自动模式使用官方 `acme.sh` 签发和续期证书，不会强制停止占用 80 端口的进程
@@ -70,15 +70,19 @@ bash <(curl -fsSL https://raw.githubusercontent.com/zxyszx/NewSzxcn-Email/main/i
 sudo newszxcn-email update
 ```
 
-命令行更新会保留当前镜像、备份数据库并执行健康检查。需要回滚时运行：
+命令行更新会创建完整回滚快照、校验数据库备份并执行健康检查。需要恢复上次更新前的镜像、数据库和配置时运行：
 
 ```bash
 sudo newszxcn-email rollback
 ```
 
+手动回滚会先要求确认，并额外备份当前数据库，再恢复更新前版本。回滚后的镜像会保持锁定，直到下一次明确执行更新。
+
 常用运维命令：
 
 ```bash
+sudo ns
+sudo newszxcn-email guide
 sudo newszxcn-email status
 sudo newszxcn-email logs
 sudo newszxcn-email restart
@@ -86,7 +90,7 @@ sudo newszxcn-email certificate
 sudo newszxcn-email uninstall
 ```
 
-`uninstall` 会移除容器和自动生成的 Nginx 配置，但不删除 `/opt/newszxcn-email` 中的配置、证书、数据库与邮件。
+`uninstall` 会移除容器和自动生成的 Nginx 配置，但不删除 `/opt/newszxcn-email` 中的配置、证书、数据库与邮件。卸载时可以单独停止当前域名的 acme.sh 自动续期，不会影响 acme.sh 管理的其他域名。
 
 ## DNS 与端口
 
diff --git a/apps/web/src/pages/mail.tsx b/apps/web/src/pages/mail.tsx
index c3e8f16..2a05108 100644
--- a/apps/web/src/pages/mail.tsx
+++ b/apps/web/src/pages/mail.tsx
@@ -174,7 +174,6 @@ export function MailPage() {
   const canDownloadAttachments = hasPermission(user, "mail.attachments.download")
   const canManageSignatures = hasPermission(user, "mail.signatures.manage")
   const canViewUnknownMail = user?.role === "admin"
-  const canManageMailboxes = hasPermission(user, "admin.mailboxes.view")
   const publicSettings = useQuery({ queryKey: ["public-settings"], queryFn: api.publicSettings })
   const externalImapEnabled = publicSettings.data?.externalImapEnabled ?? false
 
@@ -1469,7 +1468,7 @@ export function MailPage() {
   ) : !canReadMail ? (
     <PermissionEmptyState title="无邮件查看权限" description="当前账号可以访问邮箱前台，但未开启邮件查看权限。" onOpenSettings={openSettings} />
   ) : !mailboxList.isLoading && !hasMailboxes && mailView !== "unknown" ? (
-    <NoMailboxState onManageMailboxes={() => navigate(canManageMailboxes ? "/admin?section=mailboxes" : "/profile?tab=mailboxes")} />
+    <NoMailboxState onManageMailboxes={() => navigate("/profile?tab=mailboxes")} />
   ) : mailView === "scheduled" && canScheduleMail ? (
     <ScheduledSendView
       compact={compactMailLayout}
diff --git a/deploy/README.md b/deploy/README.md
index b527ecf..f3c84be 100644
--- a/deploy/README.md
+++ b/deploy/README.md
@@ -15,11 +15,14 @@ sudo newszxcn-email update
 sudo newszxcn-email status
 sudo newszxcn-email logs
 sudo newszxcn-email rollback
+sudo newszxcn-email guide
 ```
 
 一键安装会把配置和数据放在 `/opt/newszxcn-email`，并部署内部 Watchtower 更新服务。该服务不映射公网端口，仅接受带随机令牌的容器内请求；后台“立即更新”也只允许超级管理员执行。
 
-首次安装会依次询问防火墙模式、邮件服务器域名、管理员用户名/密码和 Web 部署方式。自动 Web 模式会把容器绑定到 `127.0.0.1:8088`，配置宿主机 Nginx，并使用官方 `acme.sh` 申请和续期证书。自定义管理员密码最少 6 位，留空则生成 12 位密码。
+首次安装会依次询问防火墙模式、邮件服务器域名、管理员用户名/密码和 Web 部署方式。防火墙可以选择自动添加邮局必要端口规则或保留现有规则，不会清空服务器已有防火墙。自动 Web 模式会把容器绑定到 `127.0.0.1:8088`，配置宿主机 Nginx，并使用官方 `acme.sh` 申请和续期证书。自定义管理员密码最少 6 位，留空则生成 12 位密码。
+
+安装后输入 `ns` 可以打开统一管理菜单。更新前会创建包含数据库、镜像、Compose、环境、安装脚本和 Nginx 的回滚快照；更新或健康检查失败时会自动恢复。手动完整回滚前还会单独备份当前数据库，回滚镜像会保持锁定到下一次更新。
 
 ## 最简单部署：单容器镜像版
 
diff --git a/docs/GUIDE.md b/docs/GUIDE.md
index 860b1f8..741bb4f 100644
--- a/docs/GUIDE.md
+++ b/docs/GUIDE.md
@@ -88,9 +88,11 @@ sudo newszxcn-email certificate
 重新打开安装与运维菜单：
 
 ```bash
-bash <(curl -fsSL https://raw.githubusercontent.com/zxyszx/NewSzxcn-Email/main/install.sh)
+sudo ns
 ```
 
+也可以执行 `sudo newszxcn-email menu`，或重新运行一键安装命令。
+
 常用命令：
 
 ```bash
@@ -100,9 +102,12 @@ sudo newszxcn-email restart
 sudo newszxcn-email logs
 sudo newszxcn-email certificate
 sudo newszxcn-email rollback
+sudo newszxcn-email guide
 ```
 
-命令行更新会备份 SQLite 数据库、拉取最新镜像并执行健康检查。当前 `rollback` 命令用于恢复上次命令行更新前保存的 Docker 镜像。
+命令行更新会创建完整回滚快照、校验 SQLite 数据库备份、拉取最新镜像并执行健康检查。`rollback` 命令会先备份当前数据库并要求确认，然后恢复上次更新前的镜像、数据库、Compose、环境、安装脚本和 Nginx 配置。回滚镜像会保持锁定，下一次执行更新时解除。
+
+`guide` 命令会读取当前安装地址、管理员用户名、证书到期时间和 acme.sh 续期状态，重新生成仅 root 可读的 `/root/newszxcn-email-guide.txt`。
 
 超级管理员也可以点击管理后台侧栏中的版本号，在版本更新页面检查并安装新版本。
 
diff --git a/install.sh b/install.sh
index 0934fb9..2d7027e 100755
--- a/install.sh
+++ b/install.sh
@@ -6,9 +6,14 @@ RAW_BASE="https://raw.githubusercontent.com/${REPOSITORY}/main"
 INSTALL_DIR="${LANQIN_INSTALL_DIR:-/opt/newszxcn-email}"
 COMMAND="${1:-menu}"
 ROLLBACK_FILE="${INSTALL_DIR}/.rollback-image"
+ROLLBACK_POINTER="${INSTALL_DIR}/.rollback-manifest"
+RUNTIME_IMAGE_PIN="${INSTALL_DIR}/.rollback-runtime-image"
 NGINX_CONFIG="/etc/nginx/conf.d/newszxcn-email.conf"
 ACME_WEBROOT="/var/www/newszxcn-acme"
 CERT_DIR="${INSTALL_DIR}/certs"
+GUIDE_FILE="/root/newszxcn-email-guide.txt"
+CLI_PATH="${LANQIN_CLI_PATH:-/usr/local/bin/newszxcn-email}"
+CLI_ALIAS_PATH="${LANQIN_CLI_ALIAS_PATH:-/usr/local/bin/ns}"
 
 log() { printf '\033[1;34m[NewSzxcn]\033[0m %s\n' "$*"; }
 success() { printf '\033[1;32m[完成]\033[0m %s\n' "$*"; }
@@ -28,7 +33,8 @@ NewSzxcn Email 管理命令
   logs        持续查看运行日志
   restart     重启服务并重载 Nginx
   certificate 申请或续期自动模式的 SSL 证书
-  rollback    回滚到上次命令行更新前的镜像
+  rollback    回滚到上次更新前版本
+  guide       显示并更新 NewSzxcn 邮箱指南
   uninstall   停止并移除容器，保留邮件与配置
 EOF
 }
@@ -68,31 +74,93 @@ ensure_docker() {
 }
 
 compose() {
-  docker compose --project-directory "${INSTALL_DIR}" -f "${INSTALL_DIR}/docker-compose.yml" "$@"
+  local runtime_image=""
+  if [[ -s "${RUNTIME_IMAGE_PIN}" ]]; then
+    runtime_image="$(tr -d '\r\n' < "${RUNTIME_IMAGE_PIN}")"
+  fi
+  if [[ -n "${runtime_image}" ]]; then
+    LANQIN_IMAGE="${runtime_image}" docker compose --project-directory "${INSTALL_DIR}" -f "${INSTALL_DIR}/docker-compose.yml" "$@"
+  else
+    docker compose --project-directory "${INSTALL_DIR}" -f "${INSTALL_DIR}/docker-compose.yml" "$@"
+  fi
+}
+
+clear_runtime_image_pin() {
+  rm -f "${RUNTIME_IMAGE_PIN}"
 }
 
 script_dir() {
   cd "$(dirname "${BASH_SOURCE[0]}")" 2>/dev/null && pwd
 }
 
-refresh_assets() {
+stage_assets() {
   local source_dir local_source="false"
+  local compose_new env_example_new installer_new
   source_dir="$(script_dir || true)"
   if [[ -n "${BASH_SOURCE[0]:-}" && -f "${BASH_SOURCE[0]}" && "${BASH_SOURCE[0]}" != /dev/fd/* ]]; then
     local_source="true"
   fi
   install -d -m 0755 "${INSTALL_DIR}"
+  compose_new="${INSTALL_DIR}/.docker-compose.yml.new"
+  env_example_new="${INSTALL_DIR}/.env.example.new"
+  installer_new="${INSTALL_DIR}/.install.sh.new"
+  rm -f "${compose_new}" "${env_example_new}" "${installer_new}"
   if [[ "${local_source}" == "true" && -f "${source_dir}/deploy/docker-compose.yml" && -f "${source_dir}/deploy/.env.example" ]]; then
-    install -m 0644 "${source_dir}/deploy/docker-compose.yml" "${INSTALL_DIR}/docker-compose.yml"
-    install -m 0644 "${source_dir}/deploy/.env.example" "${INSTALL_DIR}/.env.example"
-    install -m 0755 "${source_dir}/install.sh" /usr/local/bin/newszxcn-email
+    install -m 0644 "${source_dir}/deploy/docker-compose.yml" "${compose_new}"
+    install -m 0644 "${source_dir}/deploy/.env.example" "${env_example_new}"
+    install -m 0755 "${source_dir}/install.sh" "${installer_new}"
   else
-    curl -fsSL "${RAW_BASE}/deploy/docker-compose.yml" -o "${INSTALL_DIR}/docker-compose.yml"
-    curl -fsSL "${RAW_BASE}/deploy/.env.example" -o "${INSTALL_DIR}/.env.example"
-    curl -fsSL "${RAW_BASE}/install.sh" -o /usr/local/bin/newszxcn-email.new
-    chmod 0755 /usr/local/bin/newszxcn-email.new
-    mv /usr/local/bin/newszxcn-email.new /usr/local/bin/newszxcn-email
+    curl -fsSL "${RAW_BASE}/deploy/docker-compose.yml" -o "${compose_new}"
+    curl -fsSL "${RAW_BASE}/deploy/.env.example" -o "${env_example_new}"
+    curl -fsSL "${RAW_BASE}/install.sh" -o "${installer_new}"
   fi
+  chmod 0755 "${installer_new}"
+  bash -n "${installer_new}" || fail "新版安装脚本语法检查失败，现有文件未修改。"
+  if command -v shellcheck >/dev/null 2>&1; then
+    shellcheck -x "${installer_new}" || fail "新版安装脚本 ShellCheck 未通过，现有文件未修改。"
+  fi
+  if [[ -f "${INSTALL_DIR}/.env" ]] && command -v docker >/dev/null 2>&1; then
+    docker compose --project-directory "${INSTALL_DIR}" --env-file "${INSTALL_DIR}/.env" -f "${compose_new}" config >/dev/null \
+      || fail "新版 Docker Compose 配置检查失败，现有文件未修改。"
+  fi
+}
+
+apply_staged_assets() {
+  install -m 0644 "${INSTALL_DIR}/.docker-compose.yml.new" "${INSTALL_DIR}/docker-compose.yml" || return 1
+  install -m 0644 "${INSTALL_DIR}/.env.example.new" "${INSTALL_DIR}/.env.example" || return 1
+  install -m 0755 "${INSTALL_DIR}/.install.sh.new" "${CLI_PATH}.new" || return 1
+  mv "${CLI_PATH}.new" "${CLI_PATH}" || return 1
+  rm -f "${INSTALL_DIR}/.docker-compose.yml.new" "${INSTALL_DIR}/.env.example.new" "${INSTALL_DIR}/.install.sh.new"
+}
+
+ensure_cli_alias() {
+  local target="${CLI_PATH}" alias_path="${CLI_ALIAS_PATH}" existing
+  [[ -x "${target}" ]] || return 0
+  if [[ -L "${alias_path}" ]]; then
+    existing="$(readlink "${alias_path}" 2>/dev/null || true)"
+    if [[ "${existing}" == "${target}" ]]; then
+      return 0
+    fi
+    warn "未修改 ${alias_path}：现有符号链接指向 ${existing:-未知目标}。"
+    return 0
+  fi
+  if [[ -e "${alias_path}" ]]; then
+    warn "未创建快捷命令 ns：${alias_path} 已被其他文件占用。"
+    return 0
+  fi
+  existing="$(type -P ns 2>/dev/null || true)"
+  if [[ -n "${existing}" && "${existing}" != "${alias_path}" ]]; then
+    warn "未创建快捷命令 ns：系统中已存在 ${existing}。"
+    return 0
+  fi
+  ln -s "${target}" "${alias_path}"
+  success "快捷命令已创建：输入 ns 可打开管理菜单。"
+}
+
+refresh_assets() {
+  stage_assets
+  apply_staged_assets
+  ensure_cli_alias
 }
 
 random_secret() {
@@ -165,7 +233,7 @@ prompt_choice() {
 }
 
 prompt_menu_choice() {
-  local default_value="$1" value="${LANQIN_MENU_ACTION:-}"
+  local default_value="$1" max_value="${2:-10}" value="${LANQIN_MENU_ACTION:-}"
   if [[ -z "${value}" ]] && ! has_tty; then
     fail "非交互环境请直接使用 install、update、status 等子命令。"
   fi
@@ -174,13 +242,13 @@ prompt_menu_choice() {
       read -r -p "请选择 [${default_value}]: " value </dev/tty
     fi
     value="${value:-${default_value}}"
-    if [[ "${value}" =~ ^[0-9]$ ]]; then
+    if [[ "${value}" =~ ^[0-9]+$ ]] && (( value >= 0 && value <= max_value )); then
       printf '%s' "${value}"
       return
     fi
-    prompt_text "[提示] 请输入 0 至 9。\n"
+    prompt_text "[提示] 请输入 0 至 ${max_value}。\n"
     value=""
-    has_tty || fail "LANQIN_MENU_ACTION 必须设置为 0 至 9。"
+    has_tty || fail "LANQIN_MENU_ACTION 必须设置为 0 至 ${max_value}。"
   done
 }
 
@@ -258,8 +326,8 @@ configure_first_install() {
   fi
 
   local firewall_mode hostname admin_username admin_password web_mode public_url update_token
-  prompt_text '\n防火墙配置 [1]：\n1. 仅开放邮局必要端口（推荐）\n2. 保留现有防火墙，由用户自行配置\n3. 开放全部端口（不推荐）\n'
-  firewall_mode="$(prompt_choice LANQIN_INSTALL_FIREWALL_MODE "请选择 [1]: " "1")"
+  prompt_text '\n防火墙配置 [1]：\n1. 自动添加邮局必要端口规则（推荐）\n2. 保留现有防火墙，由用户自行配置\n'
+  firewall_mode="$(prompt_choice LANQIN_INSTALL_FIREWALL_MODE "请选择 [1]: " "1" "2")"
 
   hostname="$(prompt_value LANQIN_PUBLIC_HOSTNAME "邮件服务器域名，例如 mail.example.com" "")"
   valid_hostname "${hostname}" || fail "邮件服务器域名格式不正确。"
@@ -343,7 +411,7 @@ configure_restricted_firewall() {
       firewall-cmd --permanent --add-port="${ssh_port}/tcp" >/dev/null
     done
     firewall-cmd --reload >/dev/null
-    success "firewalld 已仅开放 SSH 和邮局必要端口。"
+    success "firewalld 已添加 SSH 和邮局必要端口规则。"
     return
   fi
 
@@ -355,36 +423,17 @@ configure_restricted_firewall() {
       ufw allow "${ssh_port}/tcp" >/dev/null
     done
     ufw --force enable >/dev/null
-    success "UFW 已开放 SSH 和邮局必要端口。"
+    success "UFW 已添加 SSH 和邮局必要端口规则。"
     return
   fi
   fail "没有找到可管理的 UFW 或 firewalld。"
 }
 
-configure_open_firewall() {
-  warn "正在按选择开放全部端口，请同时检查云厂商安全组。"
-  if command -v ufw >/dev/null 2>&1; then
-    ufw --force disable >/dev/null 2>&1 || true
-  fi
-  if command -v systemctl >/dev/null 2>&1; then
-    systemctl disable --now firewalld >/dev/null 2>&1 || true
-  fi
-  if command -v iptables >/dev/null 2>&1; then
-    iptables -P INPUT ACCEPT
-    iptables -F INPUT
-  fi
-  if command -v ip6tables >/dev/null 2>&1; then
-    ip6tables -P INPUT ACCEPT
-    ip6tables -F INPUT
-  fi
-  success "主机防火墙已调整为开放入站；云厂商安全组仍需单独配置。"
-}
-
 configure_firewall() {
   case "$(env_value LANQIN_INSTALL_FIREWALL_MODE || true)" in
     1) configure_restricted_firewall ;;
     2) warn "已保留现有防火墙，请自行开放 SSH、25、80、443、465、587、993、995/TCP。" ;;
-    3) configure_open_firewall ;;
+    3) warn "检测到旧版开放全部端口配置。为避免破坏现有安全规则，本次不再修改防火墙。" ;;
     "") warn "旧版安装未记录防火墙模式，本次不修改防火墙。" ;;
     *) fail "防火墙模式配置无效。" ;;
   esac
@@ -415,6 +464,16 @@ ensure_nginx() {
   fi
 }
 
+reload_nginx() {
+  command -v nginx >/dev/null 2>&1 || return 0
+  nginx -t >/dev/null 2>&1 || return 1
+  if command -v systemctl >/dev/null 2>&1; then
+    systemctl reload nginx
+  else
+    nginx -s reload
+  fi
+}
+
 write_nginx_http_config() {
   local hostname tmp
   hostname="$(env_value LANQIN_PUBLIC_HOSTNAME)"
@@ -505,6 +564,7 @@ EOF
 }
 
 ensure_acme() {
+  ensure_cron_scheduler
   if [[ ! -x /root/.acme.sh/acme.sh ]]; then
     local hostname
     hostname="$(env_value LANQIN_PUBLIC_HOSTNAME)"
@@ -512,6 +572,33 @@ ensure_acme() {
     curl -fsSL https://get.acme.sh | sh -s email="hostmaster@${hostname}"
   fi
   [[ -x /root/.acme.sh/acme.sh ]] || fail "acme.sh 安装失败。"
+  if ! acme_cron_enabled; then
+    /root/.acme.sh/acme.sh --install-cronjob >/dev/null || fail "acme.sh 自动续期任务安装失败。"
+  fi
+}
+
+acme_cron_enabled() {
+  command -v crontab >/dev/null 2>&1 \
+    && crontab -l 2>/dev/null | grep -Eq 'acme\.sh"?/acme\.sh[[:space:]]+--cron'
+}
+
+ensure_cron_scheduler() {
+  if ! command -v crontab >/dev/null 2>&1; then
+    if command -v apt-get >/dev/null 2>&1; then
+      install_packages cron
+    else
+      install_packages cronie
+    fi
+  fi
+  command -v crontab >/dev/null 2>&1 || fail "系统缺少 Cron，无法配置证书自动续期。"
+  if command -v systemctl >/dev/null 2>&1; then
+    systemctl enable --now cron >/dev/null 2>&1 \
+      || systemctl enable --now crond >/dev/null 2>&1 \
+      || fail "Cron 服务启动失败，无法保证证书自动续期。"
+  elif command -v service >/dev/null 2>&1; then
+    service cron start >/dev/null 2>&1 || service crond start >/dev/null 2>&1 \
+      || fail "Cron 服务启动失败，无法保证证书自动续期。"
+  fi
 }
 
 install_certificate() {
@@ -531,7 +618,7 @@ install_certificate() {
     --domain "${hostname}" \
     --fullchain-file "${CERT_DIR}/fullchain.pem" \
     --key-file "${CERT_DIR}/privkey.pem" \
-    --reloadcmd "/usr/local/bin/newszxcn-email reload" || fail "证书安装失败。请确认域名已解析到本机、80 端口可从公网访问，然后执行 newszxcn-email certificate 重试。"
+    --reloadcmd "${CLI_PATH} reload" || fail "证书安装失败。请确认域名已解析到本机、80 端口可从公网访问，然后执行 newszxcn-email certificate 重试。"
   chmod 0644 "${CERT_DIR}/fullchain.pem"
   chmod 0600 "${CERT_DIR}/privkey.pem"
   set_env LANQIN_TLS_CERT_FILE "/certs/fullchain.pem"
@@ -564,50 +651,204 @@ configure_web_mode() {
   esac
 }
 
-backup_database() {
-  local timestamp
-  timestamp="$(date -u +%Y%m%dT%H%M%SZ)"
-  if [[ -n "$(compose ps -q lanqin-email 2>/dev/null || true)" ]]; then
-    compose exec -T lanqin-email sh -c "mkdir -p /data/backups && sqlite3 /data/lanqin.db \".backup '/data/backups/cli-update-${timestamp}.db'\"" >/dev/null
-    log "数据库已备份到 data/backups/cli-update-${timestamp}.db"
+current_image_id() {
+  local container_id image_ref
+  container_id="$(compose ps -aq lanqin-email 2>/dev/null | head -n 1 || true)"
+  if [[ -n "${container_id}" ]]; then
+    docker inspect --format '{{.Image}}' "${container_id}"
+    return
   fi
+  image_ref="$(env_value LANQIN_IMAGE || true)"
+  image_ref="${image_ref:-ghcr.io/zxyszx/newszxcn-email:latest}"
+  docker image inspect --format '{{.Id}}' "${image_ref}" 2>/dev/null
 }
 
-remember_current_image() {
-  local container_id image_id rollback_tag
-  container_id="$(compose ps -q lanqin-email 2>/dev/null || true)"
-  [[ -n "${container_id}" ]] || return 0
-  image_id="$(docker inspect --format '{{.Image}}' "${container_id}")"
-  rollback_tag="newszxcn-email:rollback-$(date -u +%Y%m%d%H%M%S)"
-  docker image tag "${image_id}" "${rollback_tag}"
-  printf '%s\n' "${rollback_tag}" > "${ROLLBACK_FILE}"
+sqlite_integrity_check() {
+  local database="$1" image="$2" relative result
+  if command -v sqlite3 >/dev/null 2>&1; then
+    result="$(sqlite3 "${database}" 'PRAGMA integrity_check;' 2>/dev/null || true)"
+  else
+    relative="${database#"${INSTALL_DIR}"/data/}"
+    [[ "${relative}" != "${database}" ]] || return 1
+    result="$(docker run --rm --entrypoint sqlite3 -v "${INSTALL_DIR}/data:/data" "${image}" "/data/${relative}" 'PRAGMA integrity_check;' 2>/dev/null || true)"
+  fi
+  [[ "${result}" == "ok" ]]
+}
+
+backup_database() {
+  local destination="$1" image="$2" container_id running="false" relative container_destination
+  [[ -s "${INSTALL_DIR}/data/lanqin.db" ]] || { warn "未找到可备份的数据库：${INSTALL_DIR}/data/lanqin.db"; return 1; }
+  install -d -m 0700 "$(dirname "${destination}")"
+  rm -f "${destination}"
+  relative="${destination#"${INSTALL_DIR}"/data/}"
+  [[ "${relative}" != "${destination}" ]] || { warn "数据库备份必须保存在 ${INSTALL_DIR}/data 内。"; return 1; }
+  container_destination="/data/${relative}"
+  container_id="$(compose ps -aq lanqin-email 2>/dev/null | head -n 1 || true)"
+  if [[ -n "${container_id}" ]] && [[ "$(docker inspect --format '{{.State.Running}}' "${container_id}" 2>/dev/null || true)" == "true" ]]; then
+    running="true"
+  fi
+
+  if [[ "${running}" == "true" ]]; then
+    docker exec "${container_id}" sqlite3 /data/lanqin.db ".backup '${container_destination}'" >/dev/null \
+      || { warn "运行中数据库备份失败。"; return 1; }
+  elif command -v sqlite3 >/dev/null 2>&1; then
+    sqlite3 "${INSTALL_DIR}/data/lanqin.db" ".backup '${destination}'" >/dev/null \
+      || { warn "离线数据库备份失败。"; return 1; }
+  else
+    docker image inspect "${image}" >/dev/null 2>&1 || { warn "无法找到用于离线备份的旧镜像。"; return 1; }
+    docker run --rm --entrypoint sqlite3 -v "${INSTALL_DIR}/data:/data" "${image}" /data/lanqin.db ".backup '${container_destination}'" >/dev/null \
+      || { warn "离线数据库备份失败。"; return 1; }
+  fi
+
+  [[ -s "${destination}" ]] || { warn "数据库备份文件为空。"; return 1; }
+  sqlite_integrity_check "${destination}" "${image}" || { warn "数据库备份完整性检查未通过。"; return 1; }
+  log "数据库已备份并校验：${destination}"
+}
+
+create_update_snapshot() {
+  local timestamp snapshot image version pointer_tmp
+  timestamp="$(date -u +%Y%m%dT%H%M%SZ)"
+  snapshot="${INSTALL_DIR}/data/backups/cli-rollback-${timestamp}"
+  image="$(current_image_id || true)"
+  [[ -n "${image}" ]] || { warn "无法确定当前运行镜像。"; return 1; }
+  docker image inspect "${image}" >/dev/null 2>&1 || { warn "当前镜像不存在：${image}"; return 1; }
+  install -d -m 0700 "${snapshot}"
+
+  cp -p "${INSTALL_DIR}/docker-compose.yml" "${snapshot}/docker-compose.yml" || return 1
+  cp -p "${INSTALL_DIR}/.env" "${snapshot}/.env" || return 1
+  if [[ -f "${INSTALL_DIR}/.env.example" ]]; then
+    cp -p "${INSTALL_DIR}/.env.example" "${snapshot}/.env.example" || return 1
+  else
+    : > "${snapshot}/env-example.absent"
+  fi
+  if [[ -f "${CLI_PATH}" ]]; then
+    cp -p "${CLI_PATH}" "${snapshot}/newszxcn-email" || return 1
+  else
+    : > "${snapshot}/installer.absent"
+  fi
+  if [[ -f "${NGINX_CONFIG}" ]]; then
+    cp -p "${NGINX_CONFIG}" "${snapshot}/nginx.conf" || return 1
+  else
+    : > "${snapshot}/nginx.absent"
+  fi
+  if [[ -d "${CERT_DIR}" ]]; then
+    cp -a "${CERT_DIR}" "${snapshot}/certs" || return 1
+  else
+    : > "${snapshot}/certs.absent"
+  fi
+  backup_database "${snapshot}/database.db" "${image}" || return 1
+
+  version="$(docker image inspect --format '{{index .Config.Labels "org.opencontainers.image.version"}}' "${image}" 2>/dev/null || true)"
+  printf '%s\n' "${image}" > "${snapshot}/image"
+  printf '%s\n' "${version:-unknown}" > "${snapshot}/version"
+  cat > "${snapshot}/rollback-manifest.json" <<EOF
+{
+  "image": "${image}",
+  "database_backup": "${snapshot}/database.db",
+  "compose_backup": "${snapshot}/docker-compose.yml",
+  "installer_backup": "${snapshot}/newszxcn-email",
+  "version": "${version:-unknown}",
+  "created_at": "${timestamp}"
+}
+EOF
+  find "${snapshot}" -maxdepth 1 -type f -exec chmod 0600 {} +
+  pointer_tmp="${ROLLBACK_POINTER}.new"
+  printf '%s\n' "${snapshot}" > "${pointer_tmp}"
+  mv "${pointer_tmp}" "${ROLLBACK_POINTER}"
+  printf '%s\n' "${image}" > "${ROLLBACK_FILE}"
+  log "更新回滚快照已创建：${snapshot}"
+}
+
+restore_update_snapshot() {
+  local snapshot="${1:-}" restore_database="${2:-true}" image
+  if [[ -z "${snapshot}" && -f "${ROLLBACK_POINTER}" ]]; then
+    snapshot="$(tr -d '\r\n' < "${ROLLBACK_POINTER}")"
+  fi
+  [[ -d "${snapshot}" && -s "${snapshot}/database.db" && -s "${snapshot}/image" && -s "${snapshot}/docker-compose.yml" && -s "${snapshot}/.env" ]] \
+    || { warn "回滚快照不完整。"; return 1; }
+  [[ -f "${snapshot}/.env.example" || -f "${snapshot}/env-example.absent" ]] \
+    && [[ -f "${snapshot}/newszxcn-email" || -f "${snapshot}/installer.absent" ]] \
+    && [[ -f "${snapshot}/nginx.conf" || -f "${snapshot}/nginx.absent" ]] \
+    && [[ -d "${snapshot}/certs" || -f "${snapshot}/certs.absent" ]] \
+    || { warn "回滚快照缺少文件状态标记。"; return 1; }
+  image="$(tr -d '\r\n' < "${snapshot}/image")"
+  docker image inspect "${image}" >/dev/null 2>&1 || { warn "回滚镜像已不存在：${image}"; return 1; }
+  sqlite_integrity_check "${snapshot}/database.db" "${image}" || { warn "回滚数据库完整性检查未通过。"; return 1; }
+
+  log "正在恢复更新前快照：${snapshot}"
+  compose down --remove-orphans >/dev/null 2>&1 || true
+  install -m 0644 "${snapshot}/docker-compose.yml" "${INSTALL_DIR}/docker-compose.yml" || return 1
+  install -m 0600 "${snapshot}/.env" "${INSTALL_DIR}/.env" || return 1
+  if [[ -f "${snapshot}/.env.example" ]]; then
+    install -m 0644 "${snapshot}/.env.example" "${INSTALL_DIR}/.env.example" || return 1
+  elif [[ -f "${snapshot}/env-example.absent" ]]; then
+    rm -f "${INSTALL_DIR}/.env.example"
+  fi
+  if [[ -f "${snapshot}/newszxcn-email" ]]; then
+    install -m 0755 "${snapshot}/newszxcn-email" "${CLI_PATH}" || return 1
+  elif [[ -f "${snapshot}/installer.absent" ]]; then
+    rm -f "${CLI_PATH}"
+  fi
+  if [[ "${restore_database}" == "true" ]]; then
+    rm -f "${INSTALL_DIR}/data/lanqin.db-wal" "${INSTALL_DIR}/data/lanqin.db-shm"
+    install -m 0600 "${snapshot}/database.db" "${INSTALL_DIR}/data/lanqin.db" || return 1
+  fi
+  if [[ -d "${snapshot}/certs" ]]; then
+    rm -rf "${CERT_DIR}"
+    cp -a "${snapshot}/certs" "${CERT_DIR}" || return 1
+  elif [[ -f "${snapshot}/certs.absent" ]]; then
+    rm -rf "${CERT_DIR}"
+  fi
+  if [[ -f "${snapshot}/nginx.conf" ]]; then
+    install -m 0644 "${snapshot}/nginx.conf" "${NGINX_CONFIG}" || return 1
+  elif [[ -f "${snapshot}/nginx.absent" ]]; then
+    rm -f "${NGINX_CONFIG}"
+  fi
+  printf '%s\n' "${image}" > "${RUNTIME_IMAGE_PIN}"
+  chmod 0600 "${RUNTIME_IMAGE_PIN}"
+  compose up -d --remove-orphans --force-recreate || return 1
+  reload_nginx || return 1
+  wait_for_health 90 || return 1
+  ensure_cli_alias
 }
 
 do_repair_install() {
-  refresh_assets
-  ensure_update_token
-  configure_runtime_bindings
   ensure_docker
-  backup_database
-  remember_current_image
-  configure_firewall
-  prepare_directories
+  create_update_snapshot || fail "修复前备份失败，未修改现有安装。"
+  stage_assets
+  clear_runtime_image_pin
+  if ! apply_staged_assets || ! ensure_update_token || ! configure_runtime_bindings; then
+    restore_update_snapshot "" false || true
+    fail "修复准备失败，已恢复原安装。"
+  fi
+  if ! (configure_firewall && prepare_directories); then
+    restore_update_snapshot "" false || true
+    fail "修复环境准备失败，已恢复原安装。"
+  fi
   log "正在拉取并修复 NewSzxcn Email 服务..."
-  compose pull
+  if ! compose pull; then
+    restore_update_snapshot "" false || true
+    fail "修复镜像拉取失败，已恢复原安装。"
+  fi
   log "正在启动服务..."
   if ! compose up -d --remove-orphans; then
     warn "修复后容器启动失败，正在自动回滚。"
-    do_rollback
-    fail "修复失败，已回滚到原镜像。"
+    restore_update_snapshot || fail "修复失败，且自动恢复未完成，请使用回滚快照手动恢复。"
+    fail "修复失败，已恢复到修复前版本。"
   fi
   if ! wait_for_health 90; then
     warn "修复后健康检查失败，正在自动回滚。"
-    do_rollback
-    fail "修复失败，已回滚到原镜像。"
+    restore_update_snapshot || fail "修复失败，且自动恢复未完成，请使用回滚快照手动恢复。"
+    fail "修复失败，已恢复到修复前版本。"
   fi
-  configure_web_mode
+  if ! (configure_web_mode); then
+    restore_update_snapshot || fail "Web 配置失败，且自动恢复未完成，请使用回滚快照手动恢复。"
+    fail "Web 配置失败，已恢复到修复前版本。"
+  fi
+  generate_guide >/dev/null || warn "安装成功，但邮箱指南生成失败，可稍后执行 newszxcn-email guide 重试。"
   success "安装完成：$(env_value LANQIN_PUBLIC_BASE_URL)"
   warn "下一步请配置 MX、SPF、DKIM、DMARC，并确认 25/465/587/993/995 端口可访问。"
+  warn "输入 ns 可打开管理菜单；输入 newszxcn-email guide 可查看邮箱指南。"
 }
 
 do_install() {
@@ -629,54 +870,65 @@ do_install() {
   compose up -d --remove-orphans
   wait_for_health 90 || fail "服务未能通过健康检查，请执行 newszxcn-email logs 查看日志。"
   configure_web_mode
+  generate_guide >/dev/null || warn "安装成功，但邮箱指南生成失败，可稍后执行 newszxcn-email guide 重试。"
   success "安装完成：$(env_value LANQIN_PUBLIC_BASE_URL)"
   warn "下一步请配置 MX、SPF、DKIM、DMARC，并确认 25/465/587/993/995 端口可访问。"
+  warn "输入 ns 可打开管理菜单；输入 newszxcn-email guide 可查看邮箱指南。"
 }
 
 do_update() {
   [[ -f "${INSTALL_DIR}/.env" ]] || fail "尚未安装，请先执行 install。"
   ensure_docker
-  refresh_assets
-  ensure_update_token
-  backup_database
-  remember_current_image
+  create_update_snapshot || fail "更新前备份失败，未修改现有安装。"
+  stage_assets
+  clear_runtime_image_pin
+  if ! apply_staged_assets || ! ensure_update_token; then
+    restore_update_snapshot "" false || true
+    fail "更新文件替换失败，已恢复原安装。"
+  fi
   log "正在拉取最新版..."
-  compose pull
+  if ! compose pull; then
+    restore_update_snapshot "" false || true
+    fail "镜像拉取失败，已恢复到更新前版本。"
+  fi
   if ! compose up -d --remove-orphans; then
     warn "新版本容器启动失败，正在自动回滚。"
-    do_rollback
-    fail "更新失败，已回滚到原镜像。"
+    restore_update_snapshot || fail "更新失败，且自动恢复未完成，请使用回滚快照手动恢复。"
+    fail "更新失败，已恢复到更新前版本。"
   fi
   if ! wait_for_health 90; then
     warn "新版本健康检查失败，正在自动回滚。"
-    do_rollback
-    fail "更新失败，已回滚到原镜像。"
+    restore_update_snapshot || fail "更新失败，且自动恢复未完成，请使用回滚快照手动恢复。"
+    fail "更新失败，已恢复到更新前版本。"
   fi
+  ensure_cli_alias
+  generate_guide >/dev/null || warn "更新成功，但邮箱指南生成失败，可稍后执行 newszxcn-email guide 重试。"
   success "系统已更新，配置、邮件、证书和数据库均已保留。"
 }
 
 do_rollback() {
-  [[ -f "${ROLLBACK_FILE}" ]] || fail "没有可用的回滚镜像。"
-  local image
-  image="$(tr -d '\r\n' < "${ROLLBACK_FILE}")"
-  docker image inspect "${image}" >/dev/null 2>&1 || fail "回滚镜像已不存在：${image}"
-  log "正在回滚到 ${image}..."
-  LANQIN_IMAGE="${image}" compose up -d --no-deps --force-recreate lanqin-email
-  wait_for_health 90 || fail "回滚后服务仍未通过健康检查，请查看日志。"
-  success "已回滚到 ${image}。"
+  [[ -f "${ROLLBACK_POINTER}" ]] || fail "没有可用的完整回滚快照。"
+  local confirm="${LANQIN_ROLLBACK_CONFIRM:-}" image timestamp emergency_backup
+  if [[ -z "${confirm}" ]] && has_tty; then
+    read -r -p "回滚会用更新前数据库覆盖当前数据库，确认继续吗？[y/N]: " confirm </dev/tty
+  fi
+  [[ "${confirm}" =~ ^([Yy]|[Yy][Ee][Ss])$ ]] || { success "已取消回滚。"; return 0; }
+  image="$(current_image_id || true)"
+  [[ -n "${image}" ]] || fail "无法确定当前镜像，已取消回滚。"
+  timestamp="$(date -u +%Y%m%dT%H%M%SZ)"
+  emergency_backup="${INSTALL_DIR}/data/backups/pre-rollback-${timestamp}.db"
+  backup_database "${emergency_backup}" "${image}" || fail "当前数据库备份失败，已取消回滚。"
+  restore_update_snapshot || fail "完整回滚失败，请检查回滚快照和服务日志。"
+  log "回滚前数据库已保留：${emergency_backup}"
+  success "已恢复镜像、数据库、Compose、环境配置、安装脚本和 Nginx 配置。"
 }
 
 reload_services() {
   [[ -f "${INSTALL_DIR}/docker-compose.yml" ]] || return 0
   ensure_docker
   compose restart lanqin-email >/dev/null
-  if command -v nginx >/dev/null 2>&1 && [[ -f "${NGINX_CONFIG}" ]]; then
-    nginx -t >/dev/null
-    if command -v systemctl >/dev/null 2>&1; then
-      systemctl reload nginx
-    else
-      nginx -s reload
-    fi
+  if [[ -f "${NGINX_CONFIG}" ]]; then
+    reload_nginx || fail "Nginx 配置检查或重载失败。"
   fi
 }
 
@@ -694,9 +946,100 @@ do_certificate() {
   install_certificate
   write_nginx_https_config
   reload_services
+  generate_guide >/dev/null || warn "证书已应用，但邮箱指南生成失败，可稍后执行 newszxcn-email guide 重试。"
   success "SSL 证书已安装并应用。"
 }
 
+generate_guide() {
+  [[ -f "${INSTALL_DIR}/.env" ]] || return 1
+  local public_url admin_url hostname admin_username certificate_expiry="未安装" renewal_status="未开启" next_renewal="等待 acme.sh 生成续期计划"
+  local acme_info="" tmp
+  public_url="$(env_value LANQIN_PUBLIC_BASE_URL || true)"
+  hostname="$(env_value LANQIN_PUBLIC_HOSTNAME || true)"
+  admin_username="$(env_value LANQIN_ADMIN_USERNAME || true)"
+  public_url="${public_url:-http://${hostname}}"
+  admin_url="${public_url%/}/admin"
+
+  if [[ -s "${CERT_DIR}/fullchain.pem" ]] && command -v openssl >/dev/null 2>&1; then
+    certificate_expiry="$(openssl x509 -in "${CERT_DIR}/fullchain.pem" -noout -enddate 2>/dev/null | sed 's/^notAfter=//' || true)"
+    certificate_expiry="${certificate_expiry:-无法读取}"
+  fi
+  if [[ -x /root/.acme.sh/acme.sh ]]; then
+    acme_info="$(/root/.acme.sh/acme.sh --info --domain "${hostname}" --ecc 2>/dev/null || true)"
+    next_renewal="$(printf '%s\n' "${acme_info}" | sed -n "s/^Le_NextRenewTimeStr=['\"]*\([^'\"]*\).*/\1/p" | tail -n 1)"
+    next_renewal="${next_renewal:-等待 acme.sh 生成续期计划}"
+    if acme_cron_enabled; then
+      renewal_status="已开启"
+    else
+      renewal_status="已安装 acme.sh，但未检测到定时任务"
+    fi
+  fi
+
+  tmp="$(mktemp)"
+  cat > "${tmp}" <<EOF
+==================================================
+ NewSzxcn 邮箱指南
+==================================================
+
+【安装信息】
+
+邮箱前台：${public_url}
+管理后台：${admin_url}
+管理员账号：${admin_username:-admin}
+管理员密码：仅在安装完成时显示；修改后请使用新密码
+SSL 证书：有效期至 ${certificate_expiry}
+自动续期：${renewal_status}
+预计续期：${next_renewal}
+
+--------------------------------------------------
+一、添加邮件域名并配置 DNS
+--------------------------------------------------
+
+1. 登录管理后台，进入「域名管理」。
+2. 添加邮件域名并保存，然后点击该域名右侧的「DNS」。
+3. 在域名服务商处添加系统列出的 MX、SPF、DKIM、DMARC 记录。
+4. 返回管理后台点击「检测」，确认所有记录均已通过。
+
+--------------------------------------------------
+二、开启账号自助申请邮箱
+--------------------------------------------------
+
+1. 进入「管理后台 -> 系统设置 -> 邮件」。
+2. 开启「账号自助申请邮箱」，并勾选至少一个开放域名。
+3. 用户登录邮箱前台后，可在「设置 -> 邮箱管理」中自行申请邮箱。
+
+--------------------------------------------------
+三、开启无人收件
+--------------------------------------------------
+
+1. 进入「管理后台 -> 系统设置 -> 邮件」。
+2. 开启「无人收件」并保存。
+3. 已启用域名下未注册地址收到的邮件，只能由管理员在「未知收件」中查看。
+
+--------------------------------------------------
+四、服务器管理与更新
+--------------------------------------------------
+
+打开菜单：ns
+完整命令：newszxcn-email menu
+更新系统：newszxcn-email update
+查看状态：newszxcn-email status
+查看日志：newszxcn-email logs
+恢复版本：newszxcn-email rollback
+
+公开教程：
+https://github.com/zxyszx/NewSzxcn-Email/blob/main/docs/GUIDE.md
+EOF
+  install -m 0600 "${tmp}" "${GUIDE_FILE}"
+  rm -f "${tmp}"
+}
+
+do_guide() {
+  generate_guide || fail "尚未安装，无法生成邮箱指南。"
+  cat "${GUIDE_FILE}"
+  success "指南已更新并保存到 ${GUIDE_FILE}。"
+}
+
 do_status() {
   [[ -f "${INSTALL_DIR}/docker-compose.yml" ]] || fail "尚未安装。"
   compose ps
@@ -709,14 +1052,27 @@ do_status() {
 
 do_uninstall() {
   [[ -f "${INSTALL_DIR}/docker-compose.yml" ]] || fail "尚未安装。"
+  local confirm="${LANQIN_UNINSTALL_CONFIRM:-}" remove_renewal="${LANQIN_REMOVE_CERT_RENEWAL:-}" hostname
+  if [[ -z "${confirm}" ]] && has_tty; then
+    read -r -p "确认停止并卸载服务吗？邮件和配置将保留。[y/N]: " confirm </dev/tty
+  fi
+  [[ "${confirm}" =~ ^([Yy]|[Yy][Ee][Ss])$ ]] || { success "已取消卸载。"; return 0; }
+  hostname="$(env_value LANQIN_PUBLIC_HOSTNAME || true)"
   compose down --remove-orphans
   if [[ -f "${NGINX_CONFIG}" ]]; then
     rm -f "${NGINX_CONFIG}"
-    if command -v nginx >/dev/null 2>&1 && nginx -t >/dev/null 2>&1; then
-      if command -v systemctl >/dev/null 2>&1; then
-        systemctl reload nginx
+    reload_nginx || warn "Nginx 未能重载，请检查并手动重载。"
+  fi
+  if [[ -x /root/.acme.sh/acme.sh && -n "${hostname}" ]]; then
+    if [[ -z "${remove_renewal}" ]] && has_tty; then
+      read -r -p "是否停止 ${hostname} 的证书自动续期？[Y/n]: " remove_renewal </dev/tty
+    fi
+    remove_renewal="${remove_renewal:-y}"
+    if [[ "${remove_renewal}" =~ ^([Yy]|[Yy][Ee][Ss])$ ]]; then
+      if /root/.acme.sh/acme.sh --remove --domain "${hostname}" --ecc >/dev/null 2>&1; then
+        success "已停止 ${hostname} 的证书自动续期。"
       else
-        nginx -s reload
+        warn "未能移除 ${hostname} 的续期记录，请使用 acme.sh 手动检查。"
       fi
     fi
   fi
@@ -724,28 +1080,74 @@ do_uninstall() {
 }
 
 do_backup_reinstall() {
-  local backup_dir
+  local backup_dir failed_dir old_image
   backup_dir="${INSTALL_DIR}.backup-$(date -u +%Y%m%dT%H%M%SZ)"
+  failed_dir="${INSTALL_DIR}.failed-$(date -u +%Y%m%dT%H%M%SZ)"
 
-  if [[ -f "${INSTALL_DIR}/docker-compose.yml" ]] && command -v docker >/dev/null 2>&1; then
-    ensure_docker
-    compose down --remove-orphans
+  [[ -f "${INSTALL_DIR}/docker-compose.yml" ]] || fail "旧安装缺少 docker-compose.yml，请先选择修复现有安装。"
+  ensure_docker
+  old_image="$(current_image_id || true)"
+  [[ -n "${old_image}" ]] || fail "无法确定旧安装镜像，已取消重新安装。"
+  printf '%s\n' "${old_image}" > "${INSTALL_DIR}/.reinstall-image"
+  if [[ -f "${CLI_PATH}" ]]; then
+    cp -p "${CLI_PATH}" "${INSTALL_DIR}/.reinstall-installer"
   fi
+  if [[ -f "${NGINX_CONFIG}" ]]; then
+    cp -p "${NGINX_CONFIG}" "${INSTALL_DIR}/.reinstall-nginx.conf"
+  else
+    : > "${INSTALL_DIR}/.reinstall-nginx.absent"
+  fi
+  compose down --remove-orphans
   if [[ -f "${NGINX_CONFIG}" ]]; then
     rm -f "${NGINX_CONFIG}"
-    if command -v nginx >/dev/null 2>&1 && nginx -t >/dev/null 2>&1; then
-      if command -v systemctl >/dev/null 2>&1; then
-        systemctl reload nginx
-      else
-        nginx -s reload
-      fi
+    if ! reload_nginx; then
+      install -m 0644 "${INSTALL_DIR}/.reinstall-nginx.conf" "${NGINX_CONFIG}"
+      reload_nginx || true
+      LANQIN_IMAGE="${old_image}" compose up -d --remove-orphans --force-recreate \
+        || fail "Nginx 配置已恢复，但旧容器启动失败，请检查 ${INSTALL_DIR}。"
+      wait_for_health 90 || fail "Nginx 配置已恢复，但旧服务健康检查失败，请查看日志。"
+      fail "Nginx 重载失败，已恢复旧配置并取消重新安装。"
     fi
   fi
 
-  mv "${INSTALL_DIR}" "${backup_dir}"
+  if ! mv "${INSTALL_DIR}" "${backup_dir}"; then
+    if [[ -f "${INSTALL_DIR}/.reinstall-nginx.conf" ]]; then
+      install -m 0644 "${INSTALL_DIR}/.reinstall-nginx.conf" "${NGINX_CONFIG}"
+    fi
+    LANQIN_IMAGE="${old_image}" compose up -d --remove-orphans --force-recreate || true
+    reload_nginx || true
+    fail "旧安装目录备份失败，已取消重新安装。"
+  fi
   success "旧安装已完整备份到 ${backup_dir}。"
   log "现在开始全新安装。"
-  do_install
+  if (do_install); then
+    success "重新安装完成；旧安装备份保留在 ${backup_dir}。"
+    return 0
+  fi
+
+  warn "重新安装失败，正在自动恢复旧安装。"
+  if [[ -d "${INSTALL_DIR}" ]]; then
+    if [[ -f "${INSTALL_DIR}/docker-compose.yml" ]]; then
+      compose down --remove-orphans >/dev/null 2>&1 || true
+    fi
+    mv "${INSTALL_DIR}" "${failed_dir}"
+  fi
+  mv "${backup_dir}" "${INSTALL_DIR}" || fail "无法恢复旧安装目录，备份仍位于 ${backup_dir}。"
+  old_image="$(tr -d '\r\n' < "${INSTALL_DIR}/.reinstall-image")"
+  if [[ -f "${INSTALL_DIR}/.reinstall-installer" ]]; then
+    install -m 0755 "${INSTALL_DIR}/.reinstall-installer" "${CLI_PATH}"
+  fi
+  if [[ -f "${INSTALL_DIR}/.reinstall-nginx.conf" ]]; then
+    install -m 0644 "${INSTALL_DIR}/.reinstall-nginx.conf" "${NGINX_CONFIG}"
+  elif [[ -f "${INSTALL_DIR}/.reinstall-nginx.absent" ]]; then
+    rm -f "${NGINX_CONFIG}"
+  fi
+  LANQIN_IMAGE="${old_image}" compose up -d --remove-orphans --force-recreate \
+    || fail "旧安装目录已恢复，但旧容器启动失败，请检查 ${INSTALL_DIR}。"
+  reload_nginx || fail "旧安装目录和容器已恢复，但 Nginx 重载失败，请手动检查。"
+  wait_for_health 90 || fail "旧安装已恢复，但健康检查失败，请查看日志。"
+  ensure_cli_alias
+  fail "重新安装失败，旧安装已自动恢复。失败的新安装保存在 ${failed_dir}。"
 }
 
 do_menu() {
@@ -766,19 +1168,20 @@ do_menu() {
     prompt_text ' 状态：未安装\n'
   fi
   prompt_text '--------------------------------------------------\n'
-  prompt_text ' 1. 安装 / 重新安装（旧数据自动备份）\n'
-  prompt_text ' 2. 更新系统（数据库自动备份）\n'
-  prompt_text ' 3. 修复现有安装\n'
+  prompt_text ' 1. 安装 / 重新安装（完整备份，失败自动恢复）\n'
+  prompt_text ' 2. 更新系统（数据库备份，失败自动回滚）\n'
+  prompt_text ' 3. 检查并修复现有安装\n'
   prompt_text ' 4. 查看运行状态\n'
   prompt_text ' 5. 重启服务\n'
   prompt_text ' 6. 查看实时日志\n'
-  prompt_text ' 7. 申请或续期 SSL 证书\n'
-  prompt_text ' 8. 回滚上个命令行版本\n'
-  prompt_text ' 9. 卸载服务（保留数据）\n'
+  prompt_text ' 7. 申请、检查或续期 SSL 证书\n'
+  prompt_text ' 8. 回滚到上次更新前版本\n'
+  prompt_text ' 9. NewSzxcn 邮箱指南\n'
+  prompt_text ' 10. 卸载服务（保留数据）\n'
   prompt_text ' 0. 退出\n'
   prompt_text '==================================================\n'
 
-  choice="$(prompt_menu_choice "${default_choice}")"
+  choice="$(prompt_menu_choice "${default_choice}" "10")"
   if [[ "${choice}" != "0" && "${choice}" != "1" && "${installed}" != "true" ]]; then
     fail "尚未安装，请先选择 1。"
   fi
@@ -793,7 +1196,8 @@ do_menu() {
     6) ensure_docker; compose logs -f --tail=200 lanqin-email updater ;;
     7) do_certificate ;;
     8) ensure_docker; do_rollback ;;
-    9) ensure_docker; do_uninstall ;;
+    9) do_guide ;;
+    10) ensure_docker; do_uninstall ;;
   esac
 }
 
@@ -804,6 +1208,10 @@ if [[ "${LANQIN_SOURCE_ONLY:-false}" == "true" ]]; then
   exit 0
 fi
 
+if [[ "${EUID}" -eq 0 ]]; then
+  ensure_cli_alias
+fi
+
 case "${COMMAND}" in
   help|-h|--help) usage ;;
   menu) require_root; require_curl; do_menu ;;
@@ -815,6 +1223,7 @@ case "${COMMAND}" in
   reload) require_root; require_curl; reload_services ;;
   certificate) require_root; require_curl; do_certificate ;;
   rollback) require_root; require_curl; ensure_docker; do_rollback ;;
+  guide) require_root; require_curl; do_guide ;;
   uninstall) require_root; require_curl; ensure_docker; do_uninstall ;;
   *) usage; fail "未知命令：${COMMAND}" ;;
 esac
diff --git a/tests/install_test.sh b/tests/install_test.sh
index 40df73a..a681889 100644
--- a/tests/install_test.sh
+++ b/tests/install_test.sh
@@ -114,38 +114,341 @@ test_menu_choice() {
   assert_eq "0" "$(prompt_menu_choice 1)" "menu exit action"
   export LANQIN_MENU_ACTION=1
   assert_eq "1" "$(prompt_menu_choice 2)" "menu install action"
-  export LANQIN_MENU_ACTION=9
-  assert_eq "9" "$(prompt_menu_choice 1)" "menu uninstall action"
+  export LANQIN_MENU_ACTION=10
+  assert_eq "10" "$(prompt_menu_choice 1 10)" "menu uninstall action"
+  if (has_tty() { return 1; }; LANQIN_MENU_ACTION=11 prompt_menu_choice 1 10 >/dev/null 2>&1); then
+    fail_test "out-of-range menu action accepted"
+  fi
   unset LANQIN_MENU_ACTION
 }
 
-test_backup_reinstall_preserves_existing_directory() (
-  local temp_dir backup_dir
+test_offline_database_backup() (
+  local temp_dir destination
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/install"
+  mkdir -p "${INSTALL_DIR}/data/backups"
+  sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'CREATE TABLE test_items (id INTEGER PRIMARY KEY, value TEXT); INSERT INTO test_items(value) VALUES ("saved");'
+  compose() { return 0; }
+  destination="${INSTALL_DIR}/data/backups/offline.db"
+  backup_database "${destination}" "unused-image"
+  [[ -s "${destination}" ]] || fail_test "offline database backup missing"
+  assert_eq "saved" "$(sqlite3 "${destination}" 'SELECT value FROM test_items LIMIT 1;')" "offline database content"
+)
+
+test_guide_generation() (
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/install"
+  CERT_DIR="${INSTALL_DIR}/certs"
+  GUIDE_FILE="${temp_dir}/guide.txt"
+  mkdir -p "${CERT_DIR}"
+  cp "${ROOT_DIR}/deploy/.env.example" "${INSTALL_DIR}/.env"
+  set_env LANQIN_PUBLIC_HOSTNAME "mail.example.com"
+  set_env LANQIN_PUBLIC_BASE_URL "https://mail.example.com"
+  set_env LANQIN_ADMIN_USERNAME "admin"
+  generate_guide
+  grep -Fq '邮箱前台：https://mail.example.com' "${GUIDE_FILE}" || fail_test "guide frontend URL missing"
+  grep -Fq '管理后台：https://mail.example.com/admin' "${GUIDE_FILE}" || fail_test "guide admin URL missing"
+  grep -Fq '管理员密码：仅在安装完成时显示' "${GUIDE_FILE}" || fail_test "guide password safety text missing"
+  [[ "$(stat -f '%Lp' "${GUIDE_FILE}" 2>/dev/null || stat -c '%a' "${GUIDE_FILE}")" == "600" ]] || fail_test "guide permissions are not 600"
+)
+
+test_acme_cron_detection() (
+  crontab() {
+    printf '49 0,6,12,18 * * * "/root/.acme.sh"/acme.sh --cron --home "/root/.acme.sh" > /dev/null\n'
+  }
+  acme_cron_enabled || fail_test "quoted acme.sh Cron entry was not detected"
+)
+
+test_cli_alias_safety() (
+  local temp_dir
+  temp_dir="$(mktemp -d)"
+  CLI_PATH="${temp_dir}/newszxcn-email"
+  CLI_ALIAS_PATH="${temp_dir}/ns"
+  printf '#!/bin/sh\nexit 0\n' > "${CLI_PATH}"
+  chmod 0755 "${CLI_PATH}"
+  ensure_cli_alias
+  [[ -L "${CLI_ALIAS_PATH}" ]] || fail_test "ns alias was not created"
+  assert_eq "${CLI_PATH}" "$(readlink "${CLI_ALIAS_PATH}")" "ns alias target"
+  rm -f "${CLI_ALIAS_PATH}"
+  printf 'occupied\n' > "${CLI_ALIAS_PATH}"
+  ensure_cli_alias
+  grep -Fq 'occupied' "${CLI_ALIAS_PATH}" || fail_test "existing ns command was overwritten"
+)
+
+test_compose_runtime_image_pin() (
+  local temp_dir calls
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/install"
+  RUNTIME_IMAGE_PIN="${INSTALL_DIR}/.rollback-runtime-image"
+  calls="${temp_dir}/docker-calls"
+  mkdir -p "${INSTALL_DIR}"
+  printf 'services: {}\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'sha256:rollback-image\n' > "${RUNTIME_IMAGE_PIN}"
+  docker() {
+    printf '%s|%s\n' "${LANQIN_IMAGE:-}" "$*" >> "${calls}"
+  }
+
+  compose ps
+  grep -Fq 'sha256:rollback-image|compose ' "${calls}" || fail_test "rollback image pin was not applied to Compose"
+  clear_runtime_image_pin
+  compose ps
+  [[ "$(tail -n 1 "${calls}" | cut -d '|' -f 1)" == "" ]] || fail_test "cleared image pin still affected Compose"
+)
+
+test_update_snapshot_restore() (
+  local temp_dir snapshot
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/install"
+  CERT_DIR="${INSTALL_DIR}/certs"
+  NGINX_CONFIG="${temp_dir}/newszxcn-email.conf"
+  CLI_PATH="${temp_dir}/newszxcn-email-cli"
+  CLI_ALIAS_PATH="${temp_dir}/ns"
+  ROLLBACK_FILE="${INSTALL_DIR}/.rollback-image"
+  ROLLBACK_POINTER="${INSTALL_DIR}/.rollback-manifest"
+  RUNTIME_IMAGE_PIN="${INSTALL_DIR}/.rollback-runtime-image"
+  mkdir -p "${INSTALL_DIR}/data/backups" "${CERT_DIR}"
+  printf 'old-compose\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'LANQIN_IMAGE=ghcr.io/example/mail:latest\nOLD_ENV=yes\n' > "${INSTALL_DIR}/.env"
+  printf 'old-example\n' > "${INSTALL_DIR}/.env.example"
+  printf '#!/bin/sh\necho old-installer\n' > "${CLI_PATH}"
+  chmod 0755 "${CLI_PATH}"
+  printf 'old-nginx\n' > "${NGINX_CONFIG}"
+  printf 'old-certificate\n' > "${CERT_DIR}/fullchain.pem"
+  sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'CREATE TABLE test_items (value TEXT); INSERT INTO test_items VALUES ("before-update");'
+
+  current_image_id() { printf 'sha256:old-image\n'; }
+  docker() {
+    if [[ "$*" == *'org.opencontainers.image.version'* ]]; then
+      printf '1.2.4\n'
+    fi
+    return 0
+  }
+  compose() {
+    if [[ "${1:-}" == "up" ]]; then
+      grep -Fq 'sha256:old-image' "${RUNTIME_IMAGE_PIN}" || fail_test "restore started without image pin"
+    fi
+    return 0
+  }
+  nginx() { return 0; }
+  systemctl() { return 0; }
+  wait_for_health() { return 0; }
+  ensure_cli_alias() { return 0; }
+
+  create_update_snapshot
+  snapshot="$(tr -d '\r\n' < "${ROLLBACK_POINTER}")"
+  [[ -s "${snapshot}/rollback-manifest.json" ]] || fail_test "rollback manifest missing"
+
+  printf 'new-compose\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'NEW_ENV=yes\n' > "${INSTALL_DIR}/.env"
+  printf 'new-example\n' > "${INSTALL_DIR}/.env.example"
+  printf '#!/bin/sh\necho new-installer\n' > "${CLI_PATH}"
+  printf 'new-nginx\n' > "${NGINX_CONFIG}"
+  printf 'new-certificate\n' > "${CERT_DIR}/fullchain.pem"
+  sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'DELETE FROM test_items; INSERT INTO test_items VALUES ("after-update");'
+
+  restore_update_snapshot "${snapshot}"
+  grep -Fq 'old-compose' "${INSTALL_DIR}/docker-compose.yml" || fail_test "Compose file was not restored"
+  grep -Fq 'OLD_ENV=yes' "${INSTALL_DIR}/.env" || fail_test "environment file was not restored"
+  grep -Fq 'old-example' "${INSTALL_DIR}/.env.example" || fail_test "environment example was not restored"
+  grep -Fq 'old-installer' "${CLI_PATH}" || fail_test "installer was not restored"
+  grep -Fq 'old-nginx' "${NGINX_CONFIG}" || fail_test "Nginx configuration was not restored"
+  grep -Fq 'old-certificate' "${CERT_DIR}/fullchain.pem" || fail_test "certificate was not restored"
+  assert_eq "before-update" "$(sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'SELECT value FROM test_items;')" "restored database content"
+  assert_eq "sha256:old-image" "$(tr -d '\r\n' < "${RUNTIME_IMAGE_PIN}")" "restored runtime image pin"
+)
+
+test_snapshot_restores_absent_optional_files() (
+  local temp_dir snapshot
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/install"
+  CERT_DIR="${INSTALL_DIR}/certs"
+  NGINX_CONFIG="${temp_dir}/newszxcn-email.conf"
+  CLI_PATH="${temp_dir}/newszxcn-email-cli"
+  CLI_ALIAS_PATH="${temp_dir}/ns"
+  ROLLBACK_FILE="${INSTALL_DIR}/.rollback-image"
+  ROLLBACK_POINTER="${INSTALL_DIR}/.rollback-manifest"
+  RUNTIME_IMAGE_PIN="${INSTALL_DIR}/.rollback-runtime-image"
+  mkdir -p "${INSTALL_DIR}/data/backups"
+  printf 'services: {}\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'LANQIN_IMAGE=ghcr.io/example/mail:latest\n' > "${INSTALL_DIR}/.env"
+  sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'CREATE TABLE test_items (value TEXT); INSERT INTO test_items VALUES ("saved");'
+
+  current_image_id() { printf 'sha256:old-image\n'; }
+  docker() { return 0; }
+  compose() { return 0; }
+  nginx() { return 0; }
+  systemctl() { return 0; }
+  wait_for_health() { return 0; }
+  ensure_cli_alias() { return 0; }
+
+  create_update_snapshot
+  snapshot="$(tr -d '\r\n' < "${ROLLBACK_POINTER}")"
+  [[ -f "${snapshot}/env-example.absent" ]] || fail_test "missing env example marker"
+  [[ -f "${snapshot}/installer.absent" ]] || fail_test "missing installer marker"
+  [[ -f "${snapshot}/nginx.absent" ]] || fail_test "missing Nginx marker"
+  [[ -f "${snapshot}/certs.absent" ]] || fail_test "missing certificate marker"
+
+  mkdir -p "${CERT_DIR}"
+  printf 'new-example\n' > "${INSTALL_DIR}/.env.example"
+  printf '#!/bin/sh\n' > "${CLI_PATH}"
+  printf 'new-nginx\n' > "${NGINX_CONFIG}"
+  printf 'new-certificate\n' > "${CERT_DIR}/fullchain.pem"
+  restore_update_snapshot "${snapshot}"
+  [[ ! -e "${INSTALL_DIR}/.env.example" ]] || fail_test "new env example survived rollback"
+  [[ ! -e "${CLI_PATH}" ]] || fail_test "new installer survived rollback"
+  [[ ! -e "${NGINX_CONFIG}" ]] || fail_test "new Nginx configuration survived rollback"
+  [[ ! -e "${CERT_DIR}" ]] || fail_test "new certificate directory survived rollback"
+)
+
+test_pre_start_restore_preserves_current_database() (
+  local temp_dir snapshot
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/install"
+  CERT_DIR="${INSTALL_DIR}/certs"
+  NGINX_CONFIG="${temp_dir}/newszxcn-email.conf"
+  CLI_PATH="${temp_dir}/newszxcn-email-cli"
+  CLI_ALIAS_PATH="${temp_dir}/ns"
+  ROLLBACK_FILE="${INSTALL_DIR}/.rollback-image"
+  ROLLBACK_POINTER="${INSTALL_DIR}/.rollback-manifest"
+  RUNTIME_IMAGE_PIN="${INSTALL_DIR}/.rollback-runtime-image"
+  mkdir -p "${INSTALL_DIR}/data/backups"
+  printf 'services: {}\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'LANQIN_IMAGE=ghcr.io/example/mail:latest\n' > "${INSTALL_DIR}/.env"
+  sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'CREATE TABLE received_mail (subject TEXT); INSERT INTO received_mail VALUES ("before-snapshot");'
+
+  current_image_id() { printf 'sha256:old-image\n'; }
+  docker() { return 0; }
+  compose() { return 0; }
+  reload_nginx() { return 0; }
+  wait_for_health() { return 0; }
+  ensure_cli_alias() { return 0; }
+
+  create_update_snapshot
+  snapshot="$(tr -d '\r\n' < "${ROLLBACK_POINTER}")"
+  sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'INSERT INTO received_mail VALUES ("received-during-pull");'
+  restore_update_snapshot "${snapshot}" false
+  assert_eq "2" "$(sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'SELECT COUNT(*) FROM received_mail;')" "database preserved before new container start"
+  assert_eq "received-during-pull" "$(sqlite3 "${INSTALL_DIR}/data/lanqin.db" 'SELECT subject FROM received_mail ORDER BY rowid DESC LIMIT 1;')" "mail received during pull"
+)
+
+test_failed_asset_validation_preserves_production() (
+  local temp_dir source_dir
+  temp_dir="$(mktemp -d)"
+  source_dir="${temp_dir}/source"
+  INSTALL_DIR="${temp_dir}/install"
+  CLI_PATH="${temp_dir}/newszxcn-email-cli"
+  RUNTIME_IMAGE_PIN="${INSTALL_DIR}/.rollback-runtime-image"
+  mkdir -p "${source_dir}/deploy" "${INSTALL_DIR}"
+  printf 'old-compose\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'OLD_ENV=yes\n' > "${INSTALL_DIR}/.env"
+  printf 'old-example\n' > "${INSTALL_DIR}/.env.example"
+  printf '#!/bin/sh\necho old-installer\n' > "${CLI_PATH}"
+  printf 'sha256:pinned-image\n' > "${RUNTIME_IMAGE_PIN}"
+  printf 'invalid compose\n' > "${source_dir}/deploy/docker-compose.yml"
+  cp "${ROOT_DIR}/deploy/.env.example" "${source_dir}/deploy/.env.example"
+  cp "${ROOT_DIR}/install.sh" "${source_dir}/install.sh"
+
+  script_dir() { printf '%s\n' "${source_dir}"; }
+  docker() { return 1; }
+  if (stage_assets >/dev/null 2>&1); then
+    fail_test "invalid Compose file passed staging validation"
+  fi
+  grep -Fq 'old-compose' "${INSTALL_DIR}/docker-compose.yml" || fail_test "production Compose changed after failed validation"
+  grep -Fq 'old-example' "${INSTALL_DIR}/.env.example" || fail_test "production env example changed after failed validation"
+  grep -Fq 'old-installer' "${CLI_PATH}" || fail_test "production installer changed after failed validation"
+  grep -Fq 'sha256:pinned-image' "${RUNTIME_IMAGE_PIN}" || fail_test "runtime image pin changed after failed validation"
+)
+
+test_backup_reinstall_restores_on_failure() (
+  local temp_dir failed_dir
   temp_dir="$(mktemp -d)"
   INSTALL_DIR="${temp_dir}/newszxcn-email"
   NGINX_CONFIG="${temp_dir}/newszxcn-email.conf"
+  CLI_PATH="${temp_dir}/newszxcn-email-cli"
+  CLI_ALIAS_PATH="${temp_dir}/ns"
   mkdir -p "${INSTALL_DIR}"
   printf 'existing-data\n' > "${INSTALL_DIR}/marker"
+  printf 'services: {}\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'old-nginx\n' > "${NGINX_CONFIG}"
+  printf '#!/bin/sh\nexit 0\n' > "${CLI_PATH}"
+  chmod 0755 "${CLI_PATH}"
 
+  ensure_docker() { return 0; }
+  current_image_id() { printf 'sha256:old-image\n'; }
+  compose() { return 0; }
+  nginx() { return 0; }
+  systemctl() { return 0; }
+  wait_for_health() { return 0; }
+  ensure_cli_alias() { return 0; }
   do_install() {
-    [[ ! -e "${INSTALL_DIR}" ]] || fail_test "fresh install started before old directory was moved"
+    mkdir -p "${INSTALL_DIR}"
+    printf 'failed-install\n' > "${INSTALL_DIR}/failed-marker"
+    return 1
   }
 
-  do_backup_reinstall
-  backup_dir="$(find "${temp_dir}" -maxdepth 1 -type d -name 'newszxcn-email.backup-*' -print -quit)"
-  [[ -n "${backup_dir}" ]] || fail_test "existing install backup directory missing"
-  grep -Fq 'existing-data' "${backup_dir}/marker" || fail_test "existing install data was not preserved"
+  if (do_backup_reinstall); then
+    fail_test "failed reinstall unexpectedly succeeded"
+  fi
+  grep -Fq 'existing-data' "${INSTALL_DIR}/marker" || fail_test "old install directory was not restored"
+  grep -Fq 'old-nginx' "${NGINX_CONFIG}" || fail_test "old Nginx configuration was not restored"
+  failed_dir="$(find "${temp_dir}" -maxdepth 1 -type d -name 'newszxcn-email.failed-*' -print -quit)"
+  [[ -n "${failed_dir}" ]] || fail_test "failed reinstall directory was not preserved"
+)
+
+test_backup_reinstall_recovers_from_nginx_reload_failure() (
+  local temp_dir compose_calls reload_count_file
+  temp_dir="$(mktemp -d)"
+  INSTALL_DIR="${temp_dir}/newszxcn-email"
+  NGINX_CONFIG="${temp_dir}/newszxcn-email.conf"
+  CLI_PATH="${temp_dir}/newszxcn-email-cli"
+  CLI_ALIAS_PATH="${temp_dir}/ns"
+  compose_calls="${temp_dir}/compose-calls"
+  reload_count_file="${temp_dir}/reload-count"
+  mkdir -p "${INSTALL_DIR}"
+  printf 'existing-data\n' > "${INSTALL_DIR}/marker"
+  printf 'services: {}\n' > "${INSTALL_DIR}/docker-compose.yml"
+  printf 'old-nginx\n' > "${NGINX_CONFIG}"
+  printf '0\n' > "${reload_count_file}"
+
+  ensure_docker() { return 0; }
+  current_image_id() { printf 'sha256:old-image\n'; }
+  compose() { printf '%s\n' "$*" >> "${compose_calls}"; return 0; }
+  reload_nginx() {
+    local count
+    count="$(cat "${reload_count_file}")"
+    printf '%s\n' "$((count + 1))" > "${reload_count_file}"
+    [[ "${count}" -gt 0 ]]
+  }
+  wait_for_health() { return 0; }
+  do_install() { fail_test "fresh install started after Nginx reload failure"; }
+
+  if (do_backup_reinstall >/dev/null 2>&1); then
+    fail_test "reinstall continued after Nginx reload failure"
+  fi
+  grep -Fq 'existing-data' "${INSTALL_DIR}/marker" || fail_test "old install changed after Nginx reload failure"
+  grep -Fq 'old-nginx' "${NGINX_CONFIG}" || fail_test "Nginx configuration was not restored after reload failure"
+  grep -Fq 'up -d --remove-orphans --force-recreate' "${compose_calls}" || fail_test "old containers were not restarted after Nginx reload failure"
 )
 
 test_hostname_validation
 test_password_validation
 test_install_configuration 1 1 "127.0.0.1:8088" "https://mail.example.com" "false"
 test_install_configuration 2 2 "127.0.0.1:8088" "https://mail.example.com" "false"
-test_install_configuration 3 3 "80" "http://mail.example.com" "true"
 test_nginx_configuration
 test_compose_configuration
 test_legacy_configuration_is_preserved
 test_menu_choice
-test_backup_reinstall_preserves_existing_directory
+test_offline_database_backup
+test_guide_generation
+test_acme_cron_detection
+test_cli_alias_safety
+test_compose_runtime_image_pin
+test_update_snapshot_restore
+test_snapshot_restores_absent_optional_files
+test_pre_start_restore_preserves_current_database
+test_failed_asset_validation_preserves_production
+test_backup_reinstall_restores_on_failure
+test_backup_reinstall_recovers_from_nginx_reload_failure
 
 printf 'install.sh tests passed\n'