Resolved The connection to the IMAP server failed

[andrecab93]

Server operating system version

Ubuntu 22.04.5 LTS

Plesk version and microupdate number

Plesk Obsidian 18.0.73 Update #2 Web Host Edition

Hello, since yesterday evening I have been unable to access my emails. I have tried everything and always get the error message ‘Connection to IMAP server failed.’ In Roundcube and Outlook, it just says that it is not possible to connect to the server.



I haven't changed anything, so what could it be? As far as I understand, emails are coming in normally.



Thank you.

 

[danami]

Check and make sure that the dovecot service is running properly on the server with the command:

systemctl status dovecot

 

[andrecab93]

Check and make sure that the dovecot service is running properly on the server with the command:

systemctl status dovecot

Yes, its active

 

[danami]

I recommend that you tail your maillog and then do a send a receive with your email client and check for any errors:

tail -f /var/log/maillog

 

[andrecab93]

Check and make sure that the dovecot service is running properly on the server with the command:

systemctl status dovecot

systemctl status dovecot
● dovecot.service - Dovecot IMAP/POP3 email server
Loaded: loaded (/lib/systemd/system/dovecot.service; enabled; vendor prese>
Drop-In: /usr/lib/systemd/system/dovecot.service.d
└─respawn.conf
Active: active (running) since Wed 2025-10-08 22:58:27 CEST; 11h ago
Docs: man:dovecot(1)
https://doc.dovecot.org/
Main PID: 108903 (dovecot)
Status: "v2.4.1-4 (7d8c0e5759) running"
Tasks: 6 (limit: 19097)
Memory: 12.1M
CPU: 25.716s
CGroup: /system.slice/dovecot.service
├─108903 /usr/sbin/dovecot -F
├─108904 dovecot/anvil
├─108905 dovecot/log
├─108907 dovecot/config
├─111308 dovecot/stats
└─590099 dovecot/auth

Oct 09 10:17:27 XXXXX.plesk.page dovecot[108905]: pop3>
Oct 09 10:19:34 XXXXXX.plesk.page dovecot[108905]: auth>
Oct 09 10:19:34 XXXXXX.plesk.page dovecot_authdb_plesk[>
lines 1-23...skipping...
● dovecot.service - Dovecot IMAP/POP3 email server
Loaded: loaded (/lib/systemd/system/dovecot.service; enabled; vendor preset: enabled)
Drop-In: /usr/lib/systemd/system/dovecot.service.d
└─respawn.conf
Active: active (running) since Wed 2025-10-08 22:58:27 CEST; 11h ago
Docs: man:dovecot(1)
https://doc.dovecot.org/
Main PID: 108903 (dovecot)
Status: "v2.4.1-4 (7d8c0e5759) running"
Tasks: 6 (limit: 19097)
Memory: 12.1M
CPU: 25.716s
CGroup: /system.slice/dovecot.service
├─108903 /usr/sbin/dovecot -F
├─108904 dovecot/anvil
├─108905 dovecot/log
├─108907 dovecot/config
├─111308 dovecot/stats
└─590099 dovecot/auth

 

[andrecab93]

I recommend that you tail your maillog and then do a send a receive with your email client and check for any errors:

tail -f /var/log/maillog

Whenever I try to log in here, I always get the above error, but the attempts do not appear when I try to access it. Only those attempts from random emails that do not even exist appear.

Oct 9 10:28:23 wizardly-taussig dovecot_authdb_plesk[593836]: No such user 'sales@XXXXX' in mail authorization database
Oct 9 10:28:25 wizardly-taussig dovecot: pop3-login: Login aborted: Logged out (auth failed, 1 attempts in 2 secs) (auth_failed): user=<sales@XXXXX>, method=PLAIN, rip=XXXXX, lip=XXXXX, session=<NS6XlbVAmP0k/2ID>
Oct 9 10:28:58 wizardly-taussig postfix/smtpd[594548]: connect from unknown[52.125.141.16]
Oct 9 10:28:59 wizardly-taussig postfix/smtpd[594552]: connect from unknown[52.125.141.16]
Oct 9 10:29:09 wizardly-taussig postfix/smtpd[594006]: connect from unknown[45.148.10.81]
Oct 9 10:29:09 wizardly-taussig plesk_saslauthd[599146]: listen=6, status=5, dbpath='/plesk/passwd.db', keypath='/plesk/passwd_db_key', chroot=1, unprivileged=1
Oct 9 10:29:09 wizardly-taussig plesk_saslauthd[599146]: privileges set to (114:123) (effective 114:123)
Oct 9 10:29:09 wizardly-taussig plesk_saslauthd[599146]: failed mail authentication attempt for user 'callcenter' (password len=9)
Oct 9 10:29:09 wizardly-taussig postfix/smtpd[594006]: warning: unknown[45.148.10.81]: SASL LOGIN authentication failed: authentication failure
Oct 9 10:29:09 wizardly-taussig postfix/smtpd[594006]: disconnect from unknown[45.148.10.81] ehlo=1 auth=0/1 quit=1 commands=2/3
Oct 9 10:29:19 wizardly-taussig postfix/smtpd[594548]: lost connection after EHLO from unknown[52.125.141.16]
Oct 9 10:29:19 wizardly-taussig dovecot: pop3-login: Login aborted: Connection closed: read(size=620) failed: Connection reset by peer (no auth attempts in 21 secs) (no_auth_attempts): user=<>, rip=XXXXX, lip=XXXXX, TLS: read(size=620) failed: Connection reset by peer, session=<F0itl7VADRE0fY0Q>
Oct 9 10:29:19 wizardly-taussig postfix/smtpd[594548]: disconnect from unknown[52.125.141.16] ehlo=1 commands=1
Oct 9 10:29:19 wizardly-taussig dovecot: pop3-login: Login aborted: Connection closed: read(size=317) failed: Connection reset by peer (no auth attempts in 20 secs) (no_auth_attempts): user=<>, rip=XXXXX, lip=XXXXX, TLS: read(size=317) failed: Connection reset by peer, session=<WLu/l7VAGBE0fY0Q>
Oct 9 10:29:19 wizardly-taussig postfix/smtpd[594552]: lost connection after EHLO from unknown[52.125.141.16]
Oct 9 10:29:19 wizardly-taussig postfix/smtpd[594552]: disconnect from unknown[52.125.141.16] ehlo=1 commands=1
Oct 9 10:29:19 wizardly-taussig dovecot_authdb_plesk[593836]: No such user 'service@XXXXX' in mail authorization database
Oct 9 10:29:21 wizardly-taussig dovecot: pop3-login: Login aborted: Logged out (auth failed, 1 attempts in 2 secs) (auth_failed): user=<service@XXXXX>, method=PLAIN, rip=XXXXX, lip=XXXXX, session=<l4zzmLVALglNWrmN>
Oct 9 10:29:39 wizardly-taussig plesk_saslauthd[599146]: select timeout, exiting
Oct 9 10:29:53 wizardly-taussig dovecot_authdb_plesk[593836]: No such user 'sales@XXXXX' in mail authorization database
Oct 9 10:29:55 wizardly-taussig dovecot: pop3-login: Login aborted: Logged out (auth failed, 1 attempts in 2 secs) (auth_failed): user=<sales@XXXXX>, method=PLAIN, rip=XXXXX, lip=XXXXX, session=<ZGT7mrVAHl0k/2ID>
Oct 9 10:30:58 wizardly-taussig dovecot_authdb_plesk[593836]: No such user 'comercial@XXXXX' in mail authorization database
Oct 9 10:31:00 wizardly-taussig dovecot: pop3-login: Login aborted: Logged out (auth failed, 1 attempts in 2 secs) (auth_failed): user=<comercial@XXXXX>, method=PLAIN, rip=XXXXX, lip=XXXXX, session=<c6jXnrVAxHlNWrmN>
Oct 9 10:31:15 wizardly-taussig dovecot_authdb_plesk[593836]: No such user 'info01@XXXXX' in mail authorization database
Oct 9 10:31:17 wizardly-taussig dovecot: pop3-login: Login aborted: Logged out (auth failed, 1 attempts in 6 secs) (auth_failed): user=<info01@XXXXX>, method=PLAIN, rip=XXXXX, lip=XXXXX, session=<3pOen7VANBhNWrmN>

 

[Alexander Bien]

We reported a similar error to plesk yesterday. TB could not connect/authenticate to the IMAP server anymore. SMTP is fine, webmail is fine, other clients (iphone) are fine. There was no common denominator as far as we could see. Currently awaiting feedback.

 

[andrecab93]

We reported a similar error to plesk yesterday. TB could not connect/authenticate to the IMAP server anymore. SMTP is fine, webmail is fine, other clients (iphone) are fine. There was no common denominator as far as we could see. Currently awaiting feedback.

In my case, it doesn't work anywhere, whether it's webmail, Outlook, cell phone, nothing. We can't get any access.

 

[danami]

@Alexander Bien Make sure that you have updated to Plesk Obsidian 18.0.73 Update 2 as they should have fixes for that:

From the Plesk changelog:
Fixed the issue where, after updating to Plesk Obsidian 18.0.73, Thunderbird could not send or receive emails when “Encrypted Password” was selected in the email client settings, by restoring support for the CRAM-MD5 authentication scheme. (PPPM-15147)

Change Log for Plesk Obsidian

Find out about changes, additions and updates to Plesk Obsidian on an iteration to iteration basis.

docs.plesk.com

 

[andrecab93]

I understand, something misconfigured the ports on the server that were 9993.

 

[andrecab93]

Solved, it seems that Dovecot had the wrong port. Instead of 993, it had 9993. It must have been a Plesk update that misconfigured the ports. It has now been corrected and emails are coming through.