[Dovecot] mail_max_userip_connections exceeded.

[Knute Johnson]

On 1/20/2012 4:48 PM, Joseph Tam wrote:
> Simon Brereton <simon.brereton at buongiorno.com> writes:
>
>> /var/log/mail.log.1:2490:Jan 19 12:02:55 mail dovecot: imap-login:
>> Maximum number of connections from user+IP exceeded
>> (mail_max_userip_connections): user=<user at example.com>, method=PLAIN,
>> rip=127.0.0.1, secured
>>
>> I never changed this from the default 10. When I googled this error
>> there was a thread on this list from May 2011 that indicated one would
>> need one connection per user per subscribed folder. However, I know
>> that user doesn't have 10 folders, let alone 10 subscribed folders! I
>> can increase, it but it's not going to scale well. And there are
>> people on this list with many 1000x users than I have - so how do they
>> deal with that?
>>
>> 127.0.0.1 is obviously webmail (IMP5).
>
> IMAP proxy or lack of proxy?
>
> IMAP proxy could be a problem if the user had opened more than 10 (unique)
> mailboxes. The proxy would keep this connection open until a timeout, and
> after some time, could accumulate more connections than your limit.
>
> The lack of proxy could solve your problem if for some reason your webmail
> software is not closing the IMAP connection properly (I assume IMP does a
> connect/authenticate/IMAP command/logout for every webmail operation).
> Every connection (even to the same mailbox) would open up a new connection.
> The proxy software will recognize the reconnnection and funnel it through
> its cached connection.
>
> You can lsof the user's IMAP processes (or troll through
> /proc/{imap-process} or what you have) to figure out which mailboxes it
> has opened. On my system, file descriptor 9 and 11 gives you the names
> of the index files that indicate which mailboxes are being accessed.
>
> Joseph Tam <jtam.home at gmail.com>

I'm not sure that I saw the beginning of this thread but I got the same 
error.  I traced it to the fact that my destktop and my phone email 
programs were both trying to access my imap from the same local network. 
  I changed it to 20 and I haven't seen any more problems.  I don't know 
if that would be a problem on a really heavily used server or not.

-- 


Knute Johnson