diff --git a/deploy/README.md b/deploy/README.md
index a9274d2..3527458 100644
--- a/deploy/README.md
+++ b/deploy/README.md
@@ -128,6 +128,7 @@ docker compose -f docker-compose.stack.yml -f docker-compose.stack.build.yml up
 - Rspamd 会周期性从 SQLite 导出域名 DKIM 私钥到容器内 `/var/lib/rspamd/dkim`。
 - Go API 是 Webmail 和管理后台入口；浏览器不直接连接 SMTP/IMAP/POP3。
 - Go API 会读取 `LANQIN_MAILDIR_ROOT=/var/mail/vhosts`，周期扫描 Maildir，把 Postfix/Dovecot 入站邮件同步成 Webmail 索引。
+- 第三方客户端通过 SMTP `465/587` 发信时，Postfix 会把已认证发件人的邮件自动 BCC 到 `发件人+Sent@域名`，Dovecot LMTP 会保存到该邮箱的 `Sent` 文件夹，Webmail 扫描后会显示在“已发送”。
 
 ## 邮件客户端 TLS 证书
 
diff --git a/deploy/dovecot/dovecot.conf b/deploy/dovecot/dovecot.conf
index 056b445..f6690cb 100644
--- a/deploy/dovecot/dovecot.conf
+++ b/deploy/dovecot/dovecot.conf
@@ -68,4 +68,6 @@ service auth {
 
 protocol lmtp {
   postmaster_address = postmaster@localhost
+  recipient_delimiter = +
+  lmtp_save_to_detail_mailbox = yes
 }
diff --git a/deploy/postfix/main.cf b/deploy/postfix/main.cf
index 22c8374..749be76 100644
--- a/deploy/postfix/main.cf
+++ b/deploy/postfix/main.cf
@@ -4,6 +4,7 @@ myorigin = $myhostname
 mydestination = localhost
 inet_interfaces = all
 inet_protocols = all
+recipient_delimiter = +
 
 # SQLite maps read the same LanQin DB created by the Go API.
 virtual_mailbox_domains = sqlite:/etc/postfix/sqlite-domains.cf
diff --git a/deploy/postfix/master.cf b/deploy/postfix/master.cf
index 245305a..e61413e 100644
--- a/deploy/postfix/master.cf
+++ b/deploy/postfix/master.cf
@@ -4,11 +4,13 @@ submission inet n       -       n       -       -       smtpd
   -o smtpd_tls_security_level=may
   -o smtpd_sasl_auth_enable=yes
   -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
+  -o sender_bcc_maps=sqlite:/etc/postfix/sqlite-sender-bcc.cf
 smtps     inet  n       -       n       -       -       smtpd
   -o syslog_name=postfix/smtps
   -o smtpd_tls_wrappermode=yes
   -o smtpd_sasl_auth_enable=yes
   -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
+  -o sender_bcc_maps=sqlite:/etc/postfix/sqlite-sender-bcc.cf
 pickup    unix  n       -       n       60      1       pickup
 cleanup   unix  n       -       n       -       0       cleanup
 qmgr      unix  n       -       n       300     1       qmgr
diff --git a/deploy/postfix/sqlite-sender-bcc.cf b/deploy/postfix/sqlite-sender-bcc.cf
new file mode 100644
index 0000000..d8f967d
--- /dev/null
+++ b/deploy/postfix/sqlite-sender-bcc.cf
@@ -0,0 +1,2 @@
+dbpath = /data/lanqin.db
+query = SELECT local_part || '+Sent@' || substr(address, instr(address, '@') + 1) FROM mailboxes WHERE address='%s' AND status='active'