421 service not available message AOL will, from time to time, block our servers from sending them mail. When AOL is blocking our mail, you will receive a bounce-back message indicating something like "421 SERVICE NOT AVAILABLE." This is AOL rejecting our mail. This happens because AOL customers are marking too many messages from Blastcomm customers as spam, whether they are truly spam or not (and most occasions we have seen, it's not spam but someone who didn't take the time to look closely at the message before marking it as spam). AOL has an EXTREMELY low tolerance for customer-marked spam. In fact, AOL tells us their spam tolerance is 0.4 percent. Which means AOL will only accept mail from us if the total spam messages sent to them from our mail servers is less than 0.4 messages per 100, that's only 4 messages in every 1000 messages accepted! Please understand, this is an AOL policy. In the end we are delivering the mail but they are not accepting it. We would like to assure you we have done everything within our means to prevent AOL from blocking our mail, including following their guidance on adding our mail servers to their whitelists and establishing a feedback mechanism with them so that we are notified if their customers are marking mail from us as spam, as well as taking measures to reduce and eliminate outgoing spam. We have contacted AOL's postmaster and corporate HQ on numerous occasions to resolve this issue when it happens, but have come to the conclusion that it's not that important to them. Therefore, if you find your mail from your Blastcomm account or Blastcomm hosted email domain to an AOL customer is being blocked, please notify us so we are aware of the issue, but be advised there may be very little we can do to fix the situation. We request that where possible, you notify your AOL recipients of the problem and ask that they file a complaint directly with AOL. This is the only way we believe AOL will escalate the importance of the issue.