sendmail hooks for pre-checking of over-quota imap users?

[Ken Murchison]

Scott Adkins wrote:

> I was curious if anyone has implemented a mechanism in sendmail to 
> determine
> if a user is over their Cyrus quota before attempting LMTP delivery of the
> message.  If so, how was it impemented?

You can use the Sendmail Socket Map Daemon (smmapd) that I wrote for 
Cyrus.  It should be part of 2.2.3.  In order to use this, you'll have 
to be running Sendmail 8.13 or get the patch for 8.12:

http://www.sendmail.org/~ca/email/patches/sendmail-8.12.7-socketmap-v4.patch

The daemon verifies the existence of the rcpt, the ACL and the quota at 
the RCPT TO time of the SMTP exchange.  For me, its cut down on a HUGE 
amount of garbage destined for non-existent users, thus eliminating the 
outgoing bounce messages.


> 
> In our environment, I would have to say that easily, 3/4ths of all our 
> e-mail
> hitting the LMTP server is over-quota'd e-mail.
> 
> What I have done is to create a new hash file called /etc/mail/overquota.db
> that gets updated periodically (once an hour or maybe even less) with the
> list of users currently over their quota's.  I then modified the sendmail
> queuegroup rules to check for the existence of a user in that hash file and
> move then to the overquota queue if so.
> 
> I find this better than dumping all e-mail destined for local delivery to
> the cyrus queue, and then using a queue mover to find all the messages that
> had attempted LMTP delivery, but failed with an "Over quota" message.  That
> turns out to be very expensive with regards to disk I/O and CPU 
> utilization.
> 
> Also, if anyone else has other interesting ideas on how they handle lots
> of over quota e-mail (besides shortening the time that e-mail is kept on 
> the
> server or rejecting that e-mail outright), I would be interested in hearing
> about it.
> 
> Scott


-- 
Kenneth Murchison     Oceana Matrix Ltd.
Software Engineer     21 Princeton Place
716-662-8973 x26      Orchard Park, NY 14127
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