[Dovecot] pop3-throttle

[Timo Sirainen]

On Sat, 2012-06-23 at 07:04 +0200, Emmanuel Dreyfus wrote:
> Hello
> 
> I am having a hard time with users using POP while leaving mailboxes
> of several gigabyte cumulated. This causes a lot of disk I/O and kills
> performancs for everyone. I try to encourage people migrating to 
> IMAP, but that migration will take some time, and therefore I am looking
> for alterantive ways to workaround the problem.

What mailbox format do you use? This shouldn't be a problem with for
example mdbox, probably not with sdbox either and with mbox/maildir
there are settings that can improve this.

Or are you not talking about opening the mailbox, but about clients
redownloading all the mails all the time?

> I found pop3-throttle-plugin.c, which seems a smart way to solve the 
> problem, unfortunately it comes with no documentation. I was able to 
> build it and load it, bu itsays nothing in the logs. Is there any 
> doc somewhere? Any advices on how to set it up?

It's about allowing clients to see only X new mails per Y time. But I
don't see how that would help with your problem if that's related to old
mails.

Anyway, quick docs:

"touch /etc/dovecot/pop3-throttle-enabled" to enable the throttling

plugin {
  pop3_throttle_max_msgs = 10
  pop3_throttle_max_kbytes = 1024
}

Which allows a single user to see max 10 new messages or max 1 MB of new
messages per 15 minutes, whichever limit comes first. After 15 minutes
more messages become visible again to reach the limit. The 15 minute
limit is configurable by recompiling:

#define POP3_THROTTLE_STATE_RESET_SECS (60*15)