anyway if you use other vacation tecs, make sure allready flagged spam by i.e clamav, amavis, spamassassin etc in postfix stage is not handled by your vacation service , script etc. as far i remember i gave some patch to the postfixadmin vacation script doing exact this
If you're using any antispam soft that gives every mail a spam score (like spamassassin does), you can use a strong rule for vacation replies (like "only messages with a spam score under 5 are allowed, but only those under 3 may have a vacation reply").
