Allirght, we have been inundated with an unreal amount of spam on the server lately. So, I added the black URIBL to Spam Assassin. Still didn't help. So, two questions: 1) I want to block specific @domain.tld from all email domains. Under Global Filters -> Postfix Blacklist do I select "Senders" to disable those domains from sending email to mailboxes? Or, no? In otherwords, I want to add a global filter to block @nutsviagrasex.ch from spamming any email address. Would I add @nutsviagrasex.ch as "sender" in that filter? 2) I've seen mention on the tutorials about DKIM. Would that be helpful?