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Issue SMTP server error - Failed to read the server's respnse: 'Connection refused'

doom_laur

New Pleskian
Hello!

Unfortunately, I have a very strange problem and I couldn't find any solution after hours of searching the logs and the internet.

Operating system: Ubuntu 16.04.3 LTS
Plesk version: Plesk Onyx v17.5.3_build1705170317.16 os_Ubuntu 16.04 (Plesk Onyx 17.5.3 Update #20)
Mail software: none installed at the beginning, then installed MSMTP


About 1 time per minute I get the following error in /var/log/syslog:

Code:
Sep  3 13:18:59 server wdcollect[2707]: Connection to server has been established.
Sep  3 13:18:59 server wdcollect[2707]: Failed to read the server's respnse: 'Connection refused'
Sep  3 13:18:59 server wdcollect[2707]: Connection to SMTP server has been closed.
Sep  3 13:18:59 server wdcollect[2707]: Failed to connect to all SMTP servers.
Sep  3 13:18:59 server wdcollect[2707]: Connection to server has been established.
Sep  3 13:18:59 server wdcollect[2707]: Failed to read the server's respnse: 'Connection refused'
Sep  3 13:18:59 server wdcollect[2707]: Connection to SMTP server has been closed.
Sep  3 13:18:59 server wdcollect[2707]: Failed to connect to all SMTP servers.

The thing is that I removed all mail servers because I'm using the mail server of 1&1 (my hosting company). Then I thought that I'm probably getting this error because Plesk is trying to send an email and it has no mail server. So I installed with the Plesk Installer "MSMTP (relay only)" and configured it to use the 1&1 SMTP server. Just to be sure that everything works, I tried testing the 1&1 SMTP server with both the ports 465 and 587:

Code:
ifeelgood@server:~$ nc -vz smtp.1und1.de 465
Connection to smtp.1und1.de 465 port [tcp/urd] succeeded!
ifeelgood@server:~$ nc -vz smtp.1und1.de 587
Connection to smtp.1und1.de 587 port [tcp/submission] succeeded!

However, I'm still getting the same error as before, like nothing changed. All outgoing connections are allowed by the firewall, and as you can see above, the connection works on both ports 465 and 587 - but I still get the same error, no matter which port I'm using.

To be sure that the Plesk mail components are not damaged, I tried the following, but without luck:

Code:
ifeelgood@server:~$ sudo plesk repair mail

Error messages: 0; Warnings: 0; Errors resolved: 0

Many people find the problem after checking /var/log/maillog, and that file exists on my server, but it's empty.

Since the 8 lines of error above appear once every minute, this makes finding other errors almost impossible.

Thank you in advance for your help!

EDIT: I just noticed that I posted this thread in the wrong category. I'm sorry about that. Could you please move it to "Plesk Onyx for Linux"?
 
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