Thanks for all the response.
I understand the desire to have a catch-all address, I used to do it myself a few years ago. But the aggravation eventually caused me to reevaluate whether it was worth all of the dictionary attack spam. So I setup aliases in postfix for all of the addresses that I was truly interested in monitoring and simply "5xx unknown user" the rest of them.
I don't like catch-all addresses either, and I have almost never used them myself. But our customers seems to like them sometimes, so I can't ignore their wishes. But if they are doing a dirctionary attack, wouldn't it just sent 1 time a vacation message, and next time see it already sent one today - so than ignoring it, unless they change their from address ofcourse. Or are the vacation message linked to 'from' and 'to' - so if I sent an e-mail to rene@domain.com I get vacation message reply, but if I sent another mail (same from) to rene.bakkum@domain.com I get another vacation message since it are 2 different to-addresses - even though they are linked to the same mailbox?
The reason I was searching for this option, is because I am migrating from Courier/Maildrop to Dovecot/Sieve. In maildrop I think the default configuration of the vacation messages are active for any address that was received to the mailbox, you don't specify the 'to' address. And since some of the customers are liking the catch-all boxes I was searching to be any help for them so that the migration don't cause much problems on their side. But if its not possible, its not possible! It would explain why there is not much information to find about the subject :)
Thanks again
- Rene