linux sendmail 服務器建立以後。使用telnet能夠登錄，但是outlook不能登錄 outlook： 登錄郵件服務器時出錯。“用戶名”被拒絕。 帳戶: 'mail.qiaorong.com', 服務器: 'mail.qiaorong.com', 協議: POP3, 服務器響應: '-ERR Plaintext authentication disallowed on non-secure (SSL/TLS) connections.', 端口: 110, 安全(SSL): 否, 服務器錯誤: 0x800CCC90, 錯誤號: 0x800CCC91
/var/log/maillog 日誌如下：
Oct 28 08:52:54 qiaorong dovecot: imap(qiaorong): Error: user qiaorong: Initialization failed: mail_location not set and autodetection failed: Mail storage autodetection failed with home=/home/qiaorong
Oct 28 08:52:54 qiaorong dovecot: imap(qiaorong): Error: Invalid user settings. Refer to server log for more information.
Oct 28 08:54:23 qiaorong dovecot: master: Warning: Killed with signal 15 (by pid=1455 uid=0 code=kill)
Oct 28 08:54:24 qiaorong dovecot: master: Dovecot v2.0.beta6 (3156315704ef) starting up (core dumps disabled)
Oct 28 08:57:43 qiaorong dovecot: imap-login: Disconnected: Inactivity (tried to use disabled plaintext auth): rip=192.168.1.21, lip=192.168.1.16, mpid=0
Oct 28 09:00:33 qiaorong dovecot: imap-login: Disconnected (no auth attempts): rip=192.168.1.21, lip=192.168.1.16, mpid=0
Oct 28 09:27:24 qiaorong dovecot: pop3-login: Disconnected (tried to use disabled plaintext auth): rip=192.168.1.21, lip=192.168.1.16, mpid=0
Oct 28 09:27:26 qiaorong dovecot: pop3-login: Disconnected (tried to use disabled plaintext auth): rip=192.168.1.21, lip=192.168.1.16, mpid=0 解決方法: 唉。整了這麼多天終於自己整出來了，欣欣然。這個問題主要原因是mail_location not set and autodetection failed 兩個問題關於第一個mail_location ，在/etc/dovecot/conf.d目錄下有一個10-mail.conf的文件。內容如下：
# mail_location = maildir:~/Maildir
mail_location = mbox:~/mail:INBOX=/var/mail/%u
# mail_location = mbox:/var/mail/%d/%1n/%n:INDEX=/var/indexes/%d/%1n/%n
取消註釋
關於第二個問題。還是dovecot的問題，找到/etc/dovecot/dovecot.conf 文檔，編輯裏面的內容
protocols = imap pop3 lmtp
disable_plaintext_auth=no
ssl_disable = no
取消註釋，並添加你的文件中或許沒有的內容。 [root@rhel6 ~]# tail -f /var/log/maillog
Dec 21 16:51:00 rhel6 dovecot: pop3-login: Aborted login (tried to use disabled plaintext auth): rip=192.168.50.211, lip=192.168.50.24, mpid=0 5：設置/etc/dovecot/conf.d/10-mail.conf配置文件如下：
[root@rhel6 ~]# grep -v ‘^#’ /etc/dovecot/conf.d/10-mail.conf |grep -v ‘^$’ |grep -v ‘#’
mail_location = mbox:~/mail:INBOX=/var/mail/%u
mbox_write_locks = fcntl 如未設置mail_location參數值，將會出現如下錯誤：
freebsd# telnet 192.168.50.24 110
Trying 192.168.50.24…
Connected to 192.168.50.24.
Escape character is ‘^]’.
+OK Dovecot ready.
user oracle
+OK
pass oracle
Connection closed by foreign host. [root@rhel6 ~]# tail -f /var/log/maillog
Dec 21 16:52:50 rhel6 dovecot: pop3-login: Login: user=, method=PLAIN, rip=192.168.50.211, lip=192.168.50.24, mpid=9826, secured
Dec 21 16:52:50 rhel6 dovecot: pop3(oracle): Error: user oracle: Initialization failed: mail_location not set and autodetection failed: Mail storage autodetection failed with home=/u01/oracle
Dec 21 16:52:50 rhel6 dovecot: pop3(oracle): Error: Invalid user settings. Refer to server log for more information. | 
