I'd just like to let people know how effective I'm finding the AuthorrisedTo blacklist. I've been implementing this test during the past week, and in the past 3 days 42% of all emails have been rejected by this test - which is great for me because it saves my servers resources from having to process these unnessesary emails! I'm still in the process of contacting customers to retreive their lists of valid addresses, and all so far have agreed with what we're doing and provided the lists. So I expect this 42% to increase as I turn it on for more domains! One customer has about 10 users, yet in one month received emails destined to over 6,000 different recipient addresses! This test is very simple and something I've wanted to enable for a long time, but not been able to until I've come across SF! I also have a script which pulls all SMTP addresses from an entire AD regardless of OU/Container. I originally downloaded this script, but had it modified by one of our programmers as it didn't pull email addresses for distribution groups, and did not recurse as it should.