Situation: for one of my domains, postfix (ISPConfig Server) relays mail to a GroupWise 2014 system. In case of lot of SPAM to not existent recipients groupwise end back 550 messages to postfix. In case of SPAM postfix can not deliver the 550 notification, as the original sending host it not reachable, case of fake, wrong DNS etc. So the postfix queue grows and grows up to 3 to 5 thousend in less then 3 days. Only thing I can do "postsuper -d ALL" every two days, whats no so comfortable and has the little risk to delete some good messages in the queue at that time. Searching the internet I dis not found a way to supres the 550 from GroupWise, nor in postfix. In GroupWise I have the possibilty to relay NDMs to an other mailhost, but what to do the with them, Nic to have something like an NULL mailhost, deleting all incoming mail automaticly. Thanks for hint Rainer
