[dovecot] Re: Dovecot and Quotas

[David Champion]

* On 2003.03.26, in <1048697679.31484.40.camel at rocket>,
*	"Mike Machado" <mike at innercite.com> wrote:
> I have seen this suggestion elsewhere and would be perfect. The customer
> only needs a few extra kilobytes when their quota is full, so the hard
> quota could be just a bit bigger with a long/unlimited grace. The hard
> part is to get procmail or whatever local delivery agent to stop at the
> SOFT quota. I could probably quite some funky procmail rules, but that
> will add an unwanted amount of load to an already busy system. Anyone
> know if their are some built in sendmail/procmail checking that can aide
> here?

None that I know of. Hard quotas are terrible for a mail system, in my
experience. Part of the trouble is the automation -- we run across a lot
of cases where automated management isn't very nice to users. There are
always exceptions -- Professor Jones is doing field research in Egypt,
or somesuch, and has limited access. For such cases, we want longer
quota warning periods.

We have a nightly job that checks everyone's mail usage nightly. If
someone's usage goes above what we consider good, it decrements a
counter, set initially to 7 days (5 working days). Each day that this
counter is set, it mails the user a warning that mail will be blocked
in N days, and when a counter reaches 0 it mails us, the admins, and we
run a script to block access. Part of this is sticking a helpful entry
in /etc/mail/access to block incoming mail. (We use sendmail.) So that's
where you can cause SMTP blocks, but you need your own scripts for
managing it.

There are two loopholes here -- people can still store as much mail as
they want to the server via IMAP, and people can neglect their overuse
for as long as they want to. Those might be weaknesses or advantages,
depending on how you look at it. But most people want new mail via SMTP,
too, and they don't get it until they clear their IMAP. But since we
have so many users, the relatively small number of troublesome users
never cause major trouble -- their abuses are relatively small. IOW, we
don't generally need to keep individuals reined in, just the masses.

-- 
 -D.	dgc at uchicago.edu	NSIT	University of Chicago
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