procmail autoresponder
This is a really simple autoresponder built as a set of procmail rules. It's goal is to discard all incoming messages and provide a custom, auto generated reply when needed.
# Use :0 hc if you need to retain a copy of the
# original message.
:0 h
* !^FROM_DAEMON
* !^FROM_MAILER
* !^X-Loop: autoreply
* ^Subject:.*
| (formail -rt \
-A"Precedence: junk (autoreply)" \
-A"X-Loop: autoreply" ; \
-I"From: Me <myself@mydomain.tld>" \
cat $HOME/autoreply.txt) | $SENDMAIL -t
# This rule will discard all messages not trapped
# by the autoresponder rule above. Delete it if you
# want to keep incoming messages.
:0
/dev/null
More details and information can be found in the excellent Shane Tzen's autoresponder with procmail howto.
