How to fix "imapd-ssl: Maximum connection limit
reached for ::ffff:xxx.xxx.xxx.xxx" imapd-ssl error
One of one of the mail server clients is running into issues with
secured SSL IMAP connections ( he has to use a multiple email
accounts on the same computer).
I was informed that part of the email addresses are working
correctly, however the newly created ones were failing to
authenticate even though all the
Outlook Express email
configuration was correct as well as the username and password
typed in were a real existing credentials on the vpopmail
server.
Initially I thought, something is wrong with his newly configured
emails but it seems all the settings were perfectly correct!
After a lot of wondering what might be wrong I was dumb enough not
to check my imap log files.
After checking in my
/var/log/mail.log which is the default
log file I've configured for vpopmail and some of my qmail server
services, I found the following error repeating again and
again:
imapd-ssl: Maximum connection limit reached for
::ffff:xxx.xxx.xxx.xxx" imapd-ssl error
where
xxx.xxx.xxx.xxx was the email user computer IP
address.
This issues was caused by one of my configuration settings in the
imapd-ssl and imap config file:
/usr/lib/courier-imap/etc/imapd
In
/usr/lib/courier-imap/etc/imapd there is a config segment
called
Maximum number of connections to accept from the same IP
address
Right below this commented text is the variable:
MAXPERIP=4
As you can see it seems I used some very low value for the maximum
number of connections from one and the same IP address.
I suppose my logic to set such a low value was my desire to protect
the IMAP server from Denial of Service attacks, however 4 is really
too low and causes problem, thus to solve the mail connection
issues for the user I raised the
MAXPERIP value to
50:
MAXPERIP=4
Now to force the new
imapd and
imapd-ssl services to
reload it's config I did a restart of the courier-imap, like
so:
debian:~# /etc/init.d/courier-imap restart
That's all now the error is gone and the client could easily
configure up to 50 mailbox accounts on his PC :)