Blacklist outgouing mail
A major Slovenian free e-mail provider has recently gone bust. As a result, thousands of outgoing e-mails are being deferred in our server's mail logs, as some of the hosted sites still try to send e-mail to these addresses.
Is there a way to tell postfix (through ISPConfig if possible) to completely ignore any e-mail being sent out, whose recipient belongs to a certain domain? Postfix should not try to send such messages and if possible, not even log the attempt.
I tried adding a record to "Email > Global Filters > Postfix Blacklist" with "@offending-domain.tld" as Blacklist Address and Recipient as Type. This doesn't seem to have the desired effect though.