[BlueOnyx:05233] dovecot mail_max_user_connections (imap)

[Christoph Schneeberger]

Good afternoon list,

I have got a report from a customer with ~15 mailboxes all accessed via
IMAP (TB 3.x on Win32) from behind a nat gateway that they get locked
out from time to time.
Looking in the logs I found many entries for their IP with an error
regarding dovecots mail_max_user_connections setting (which seems to
default to 10 if not set as it is in BlueOnyx):

dovecot: imap-login: Maximum number of connections from user+IP exceeded
(mail_max_userip_connections): user=<username>, method=PLAIN,
rip=x.x.x.97, lip=x.x.x.77

The simple solution would probably to just increase that value in
/etc/dovecot.conf to something like 25 or so, however I fear this might
be overwritten soon by updates through yum or changes in the GUI. On the
other hand we run much busier BlueOnyx boxes in terms of IMAP
connections and its the first time I see this problem.

So I wonder if others have seen this problem with dovecot , what others
think is a reasonable value for mail_max_user_connections (imap) without
completely defeating the purpose of the limit and last but not least if
it might be worth considering to make this setting changeable through
the GUI or at least set a slightly increased default.

Thanks for your input and oppinions in advance,
Christoph