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Issue Dovecot limit on service imap_login question

nilsringersma_nl

Basic Pleskian
Dear forum members,

I'm experiencing a problem, after some days of investigation I can't resolve this problem. Perhaps someone can provide me with some advice, it would be really appreciated. Thanks in advance.

Machine:
CentOS Linux 7.3.1611 (Core)‬
Plesk Onyx Version 17.5.3 Update #13
imap-server: dovecot

Context:
The machine is used by a company that has 35 mailboxes which are setup in Thunderbird. Multiple computers retrieve mail with the IMAP protocol. Sometimes the clients complain about being unable to connect to IMAP briefly. I can confirm the issue through Nagios which has the same problem:

vps-xxx-managed-by.xxx.nl/IMAP login is CRITICAL:
CRITICAL: Could not connect to mobico.nl: socket error: EOF


Problem:
At the exact moment of the notifications in Nagios I can see the following entry in /var/log/maillog:

Jul 18 13:19:21 vps-xxx-managed-by dovecot: master: Warning: service(imap-login): process_limit (100) reached, client connections are being dropped.

What I've done:
In plesk UI there's an option to set
Maximum number of connections (IMAP, POP3, IMAP over SSL/TLS, or POP3 over SSL/TLS) & Maximum number of connections for a user per IP address. I've upped these to 500. However after some investigation the problem was still occuring.

When reading the error message I can see that making the setting in Plesk UI changes 'service imap' but the error in the maillog shows that imap_login service is at 100. Therefore i created a file in /etc/dovecot/conf.d/test.conf with the content:

service imap_login {
service_count = 1
process_limit = 500
}

dovecot -n output
See dovecot-n.txt , as you can see the test.conf is included.

Result:
The problem still occurs and the maillog still shows "dovecot: master: Warning: service(imap-login): process_limit (100) reached, client connections are being dropped". It seems my new limit is not working.

Edit:
I also tried enabling performance mode ( LoginProcess - Dovecot Wiki ), however this was not succesfull either. The same limit of 100 was still being shown in the maillog.

Question:
Please help!
 

Attachments

  • dovecot-n.txt
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Last edited:
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