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manifestor
Asked: 2019-11-29 04:52:26 +0800 CST

Debugging postfix/dovecot: Finding out which application is trying to connect from localhost 127.0.0.1

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The problem occurs on my mail server, which apart from that works perfectly. Clients can connect via IMAP and Postfix receives and sends out emails without any hassle.

Installed software:

$> dpkg --list
ii  postfix                         3.1.12-0+deb9u1        amd64
ii  dovecot-core                    1:2.2.27-3+deb9u5      amd64
ii  dovecot-imapd                   1:2.2.27-3+deb9u5      amd64

I get the following error message every minute (and as I'm monitoring log files this is driving me crazy as I get every time an alert because of the syscall failed in my monitoring system):

Nov 27 18:30:17 localhost dovecot: imap-login:
   Disconnected (no auth attempts in 0 secs):
   user=<>, rip=127.0.0.1, lip=127.0.0.1,
   TLS handshaking: SSL_accept() syscall failed: Success,
   session=<lMywWVeYJpZ/AAAB>

As we can see the user field is empty and the request comes from localhost. Now I'm trying to debug my system and my questions are:

  • Did someone experienced the same problem? Is that really some application, which resides on the same machine, which is trying to connect or is something else causing this log message?
  • How can I find out which application is trying to connect?

Any help is much appreciated!

EDIT:

The log messages exactly before the aforementioned error message:

Nov 27 18:30:17 localhost postfix/postscreen[29370]: CONNECT from [127.0.0.1]:50844 to [127.0.0.1]:25
Nov 27 18:30:17 localhost postfix/postscreen[29370]: WHITELISTED [127.0.0.1]:50844
Nov 27 18:30:17 localhost postfix/smtpd[13455]: connect from localhost[127.0.0.1]
Nov 27 18:30:17 localhost postfix/smtpd[13455]: lost connection after CONNECT from localhost[127.0.0.1]
Nov 27 18:30:17 localhost postfix/smtpd[13455]: disconnect from localhost[127.0.0.1] commands=0/0
Nov 27 18:30:17 localhost postfix/submission/smtpd[15222]: connect from localhost[127.0.0.1]
Nov 27 18:30:17 localhost postfix/submission/smtpd[15222]: lost connection after CONNECT from localhost[127.0.0.1]
Nov 27 18:30:17 localhost postfix/submission/smtpd[15222]: disconnect from localhost[127.0.0.1] commands=0/0
postfix

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