Dovecot IMAP Connections

Hi

I’ve noticed some log entries like this recently: They are always from the same user - and I’m pretty sure he uses UserMIn Webmail for his email.

dovecot: imap-login: Maximum number of connections from user+IP exceeded (mail_max_userip_connections=10): user=postmaster@domain.com

At the same time, my server has gone into a panic-mode spin (whether coincidence, or cause, or effect - I’m not sure). The last time this happened I managed to log in, and there were several ‘miniserv.pl’ processes running from this user (at 100% cpu!).

So I’m thinking - Is there something he’s doing that makes this happen? And, why is it necessary to allow up to 10 IMAP connections from the same user? I can understand someone might have a number of devices all trying to do IMAP at the same time, but even so, 10 seems a bit generous? 10 Perl processes would be quite a hog, no?

So I’m thinking - Is there something he’s doing that makes this happen?

Yeah it’s possible it’s something that user is accidentally doing that’s causing a problem, though it’s difficult to know what. How large is their inbox?

but even so, 10 seems a bit generous? 10 Perl processes would be quite a hog, no?

Well, the way IMAP works, it’s very fond of opening new connections for new actions, and it’s common for multiple IMAP connections to be open at the same time. Having 10 connections open at a time isn’t unusual – though what is unusual is that your CPU is at 100%.

I’d be most curious to learn what exactly it is that they’re doing.

Do you notice anything unusual in the Usermin logs, in either /var/usermin/miniserv.log or /var/usermin/miniserv.error?

-Eric

In miniserv.error I see quite a few lines: “Failed to initialize SSL connection”

And also all this at one point yesterday :frowning:

Failed to initialize SSL connection
Failed to initialize SSL connection
Out of memory!
Out of memory!
Failed to initialize SSL connection
Failed to initialize SSL connection
Out of memory!
Out of memory!
Failed to initialize SSL connection
Out of memory!
Out of memory!
Out of memory!
Failed to initialize SSL connection
Out of memory!
Out of memory!
Failed to initialize SSL connection
Out of memory!
Out of memory!
Failed to initialize SSL connection
Failed to initialize SSL connection
Failed to initialize SSL connection
Failed to initialize SSL connection
Failed to initialize SSL connection
Failed to initialize SSL connection
Error: Failed to login to IMAP server : [UNAVAILABLE] Maximum number of connections from user+IP exceeded (mail_max_userip_connections=10)
Out of memory!
Out of memory!
Out of memory!

I had this problem with a client not too long ago. They bought a new phone and had it checking their email every 5 minutes, in addition to their computer, etc. :slight_smile: When you have things like cell phones, ipads, PC’s all checking the same email account, and sometimes they do it at the same times, the slots can get used up quite rapidly. Some will connect and stay connected (all day). I have all mine set to 20 connections and it fixed a lot of what you are seeing (except the SSL errors…). I haven’t noticed any performance issues due to raising the limit, but I’m sure it could.

This could be the case, if they connect everything through wifi at home.

But if the phone is just on 3/4g then it wouldn’t matter, because the connection limit is per ip address .