http://postmaster.info.aol.com/errors/554rlyir.html This is a serious problem. AOL have started a new kind of blocking where they will penalise hosts for sending to addresses at AOL that dont exist. This can be any kind of message including a bounce or undelivered report. So if you send an email to firstname.lastname@example.org and that address does not exist on their system, they will give your server a penalty point. If this happens regualarly, they will simply blacklist your server. Currently we have three servers blacklisted bay AOL for this reason. My issue with it is that I know for a fact that none of these servers are sending out spam or unsolicited mail. The problem must be with bounced mail. If a spammer sends a load of email with a faked header, pretending to be from a non existent AOL address (which happens alot), the bounce messages will be sent back to the reply address. Here is an example.... A spammer sends 1000 emails in a dictionary attack to a domain on one of our servers. The spoofed header shows a return address of email@example.com The addresses would be like this... firstname.lastname@example.org email@example.com firstname.lastname@example.org email@example.com firstname.lastname@example.org email@example.com etc etc None of those addresses exist but the spammer is bombing the domain trying to get a match. So, all the emails bounce back to firstname.lastname@example.org which of course doesnt exist. So AOL in their wisdom add penalty points to our server for sending to a non existent AOL address. Then within a week, we get blacklisted and none of our customers on that server can send email to AOL. This is the only reason I can think of for us being blacklisted - I have spent a long time looking at the servers and they simply are not sending out unsolicited mail. The whole this is a nightmare and I'm very upset about it. Especially as the AOL Postmaster can no longer be contacted 24hrs - we have to wait for the USA to get out of bed. Is anyone else experiencing this issue ?