[Dovecot] Simulating UW Snarf...

[Geo Carncross]

On Wed, 2006-02-08 at 22:18 +0100, Lorens wrote:
> > We 
> > need to never bounce mail yet deliver the mail that has built up for an 
> > over quota user as quickly as we can once that user goes below quota. 
> > If Dovecot moved the mail from /var/spool/mail/%u to the user's homedir 
> > then that is exactly what I want.  As long as it fails gracefully if the 
> > user is over quota.

This sounds like an Extremely Complicated[tm] solution is desired where
one doesn't appear to be necessary, just a bunch of little steps:

1. Have your MTA deliver messages into $HOME/Maildir

Your MTA should tempfail if delivery fails because write() failed [which
it would if the user went over quota]. Temporary failures should be
retried later.

2. If you really want to "never bounce [local] messages", consider
configuring your MTA to simply never expire local mail- although some
users consider bounces useful as it means the recipient didn't receive
the mail in a [reasonable] amount of time.

In any event, on qmail this is trivial:

(cd /var/qmail/queue/local && find . -type f) \
| awk '{ print "touch -c /var/qmail/queue/info/"$0 }' | sh

could go into your crontab and run (say) once a day or so. If you simply
wanted to rejuvenate messages that were deferred due to quotas, you
could hook something into repquota.

3. Finally, to "try as quickly as possible", consider using ngrep

ngrep -s 65535 EXPUNGE 'tcp dst port 143' 2>&1 |  awk '{ if ($0 ~ /^T/)
{ print "pkill -ALRM qmail-send" } }' | sh

Substituting the "pkill -ALRM qmail-send" for whatever you use to tell
your MTA to retry deliveries as soon as possible.


For the record, you'll note that dovecot isn't involved in any of this,
but your MTA needs to do three things:

1. The Right Thing when write() fails and we're updating the INBOX
2. Provide a way to restart at least local delivery as soon as possible
3. Provide a way to rejuvenate messages

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