Dbmail 2.0 currently support per-user (not per-address) auto-reply. I consider this severely broken because there's no loop-detection in there whatsoever.

Last year I wrote a temporary stop-gap solution in python (autoreplier.py). It will send replies from/to the same addresses only every TIMEOUT seconds.

1. install this in i.e. /usr/local/bin/autoreplier.py
2. #>install -d -o dbmail -g dbmail -m 2770 /var/cache/dbmail
3. Add a reply message

cat >> /var/cache/dbmail/paul-autoreply.eml << EOM
From: paul@no.harvesting.please.nfg.nl
Subject: vacation

I'm yonder.
---
#CU
EOM

1. Install the forward for a delivery address of your choosing,

dbmail-users -x paul@no.harvesting.please.nfg.nl -t '|/usr/local/bin/autoreplier.py -u paul
-a paul@no.harvesting.please.nfg.nl -m /var/cache/dbmail/paul-autoreply.eml'

Et voila.

1. As you return don't forget to disable this:

dbmail-users -x paul@no.harvesting.please.nfg.nl -T '|/usr/local/bin/autoreplier.py -u paul
-a paul@no.harvesting.please.nfg.nl -m /var/cache/dbmail/paul-autoreply.eml'