我在使用 POP3 从我的 VPS 接收电子邮件时遇到问题。在邮件应用中，我收到消息，表示连接失败，无论如何我都应该检查登录名和电子邮件，这很好。我尝试通过 bash 检查它：
telnet mail.inovestudio.com 110
Trying 5.135.147.5... Connected to mail.inovestudio.com. Escape character is '^]'.
+OK Dovecot ready.
USER [email protected]
+OK
PASS here_i_put_some_pass**
Connection closed by foreign host.
你知道为什么会出现这种情况吗？我该如何解决它？谢谢。
已解决：在 /etc/dovecot/conf.d/10-auth.conf 中我使用这个：
disable_plaintext_auth = yes
邮件日志
Nov 10 05:41:33 vps22346 dovecot: auth: Error: BUG: Authentication client sent unknown handshake command: REQUEST?3110993921?677?1?0b0656b72c084511c2988b99b346c1a5
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Authentication server didn't send valid SPID as expected: MECH PLAIN plaintext
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Disconnected from auth server, aborting (client-pid=677 client-id=1)
Nov 10 05:41:33 vps22346 dovecot: pop3-login: Internal login failure (pid=677 id=1) (internal failure, 1 succesful auths): user=<[email protected]>, method=LOGIN, rip=188.175.31.165, lip=5.135.147.5, mpid=680, TLS, session=<+fv6UigkNAC8rx+l>
Nov 10 05:41:33 vps22346 dovecot: auth: Warning: auth client 677 disconnected with 1 pending requests: EOF
Nov 10 05:41:33 vps22346 dovecot: auth: Error: BUG: Authentication client sent unknown handshake command: REQUEST?602800129?676?1?25bf41ba73464024b67fff41742cba4f
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Authentication server didn't send valid SPID as expected: MECH PLAIN plaintext
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Disconnected from auth server, aborting (client-pid=676 client-id=1)
Nov 10 05:41:33 vps22346 dovecot: pop3-login: Internal login failure (pid=676 id=1) (internal failure, 1 succesful auths): user=<[email protected]>, method=LOGIN, rip=188.175.31.165, lip=5.135.147.5, mpid=681, TLS, session=<LPr6UigkMwC8rx+l>
Nov 10 05:41:33 vps22346 dovecot: auth: Warning: auth client 676 disconnected with 1 pending requests: EOF
Nov 10 05:41:33 vps22346 dovecot: auth: Error: BUG: Authentication client sent unknown handshake command: REQUEST?1481113601?679?1?6be03e001c9de41da5fc46999f937597
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Authentication server didn't send valid SPID as expected: MECH PLAIN plaintext
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Disconnected from auth server, aborting (client-pid=679 client-id=1)
Nov 10 05:41:33 vps22346 dovecot: pop3-login: Internal login failure (pid=679 id=1) (internal failure, 1 succesful auths): user=<[email protected]>, method=PLAIN, rip=188.175.31.165, lip=5.135.147.5, mpid=682, TLS, session=<G9D7UigkNQC8rx+l>
Nov 10 05:41:33 vps22346 dovecot: auth: Warning: auth client 679 disconnected with 1 pending requests: EOF
Nov 10 05:41:33 vps22346 dovecot: auth: Error: BUG: Authentication client sent unknown handshake command: REQUEST?2768109569?683?1?bd65b7382983d84dbf6d3c710d7bf9d3
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Authentication server didn't send valid SPID as expected: MECH PLAIN plaintext
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Disconnected from auth server, aborting (client-pid=683 client-id=1)
Nov 10 05:41:33 vps22346 dovecot: pop3-login: Internal login failure (pid=683 id=1) (internal failure, 1 succesful auths): user=<[email protected]>, method=PLAIN, rip=188.175.31.165, lip=5.135.147.5, mpid=685, TLS, session=</r0AUygkNgC8rx+l>
Nov 10 05:41:33 vps22346 dovecot: auth: Warning: auth client 683 disconnected with 1 pending requests: EOF
Nov 10 05:41:33 vps22346 dovecot: auth: Error: BUG: Authentication client sent unknown handshake command: REQUEST?1966735361?684?1?81003e4dfc94424d81de1215228fe809
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Authentication server didn't send valid SPID as expected: MECH PLAIN plaintext
Nov 10 05:41:33 vps22346 dovecot: pop3: Error: Disconnected from auth server, aborting (client-pid=684 client-id=1)
Nov 10 05:41:33 vps22346 dovecot: pop3-login: Internal login failure (pid=684 id=1) (internal failure, 1 succesful auths): user=<[email protected]>, method=PLAIN, rip=188.175.31.165, lip=5.135.147.5, mpid=686, TLS, session=</70AUygkNwC8rx+l>
Nov 10 05:41:33 vps22346 dovecot: auth: Warning: auth client 684 disconnected with 1 pending requests: EOF
Nov 10 05:42:26 vps22346 postfix/anvil[509]: statistics: max connection rate 1/60s for (smtps:188.175.31.165) at Nov 10 05:39:06
Nov 10 05:42:26 vps22346 postfix/anvil[509]: statistics: max connection count 1 for (smtps:188.175.31.165) at Nov 10 05:39:06
Nov 10 05:42:26 vps22346 postfix/anvil[509]: statistics: max cache size 1 at Nov 10 05:39:06
当我尝试执行此操作时：service postfix restart
它返回：
[ ok ] Stopping Postfix Mail Transport Agent: postfix.
[ ok ] Starting Postfix Mail Transport Agent: postfix.
root@vps22346:/# 2015 Nov 17 09:47:16 vps22346 lda: Fatal: Internal error occurred. Refer to server log for more information.
答案1
看来 dovecot 配置为拒绝非安全身份验证，这很好。要测试，请使用
openssl s_client -connect mail.inovestudio.com:995
您应该会看到很多信息，但最后应该以
+OK Dovecot ready.
你可以尝试
USER [email protected]
PASS yourcleartextpassword