[Dovecot] mail_max_userip_connections=10

[Stan Hoeppner]

On 9/19/2011 7:36 AM, Tom Clark wrote:
> Hi Paul,
>
> It's coming from the same IP address through his ADSL. Hence he gets the
> problem with max_userip_connections.
>
> I think I tracked down the problem. He's been using K9 mail which seems to
> have a problem where it doesn't release a connection and has 1 connection
> per subscribed folder....

The reasoning behind the multiple socket communication design in the 
IMAP protocol is flawed, thus we end up with problems like yours, and 
others.  It may have looked good on the white board but it doesn't seem 
to add benefit in production--only add problems.  At least from an SA's 
perspective.  Just about every other modern internet protocol gets by 
with a single socket, and many of those applications are more complex 
than IMAP.

Multiple virtual channels are a good idea at the data link layer of WAN 
communications links, and work well there.  They're a lousy idea at the 
application layer, however, as the IMAP protocol clearly demonstrates. 
Everything IMAP does over multiple sockets could have been accomplished 
over a single socket, with no noticeable decrease in performance, but 
with fewer SA headaches and fewer server resources consumed.

I eagerly await a successor to the current version of IMAP, which will 
hopefully do away with this problematic, unnecessary, multiple socket 
nonsense.  It may be a long wait, unfortunately...

-- 
Stan