One of my users who is subscribed to yahoo groups, had the subscription turned off, because a message was being bounded.
The bounce message was 553 5.0.0 Header Error [BODY] Which is not very informative. After a bit of tracking I found out that the message was a result of test in the default sendmail.mc that checked that message id were of the format [EMAIL PROTECTED] There is RFC 2111 that says that message id should be in the format of [EMAIL PROTECTED] There is a comment saying: Enforce valid Message-Id to help stop spammers. It seems that yahoo does not in force such a check and was forwarding a spam message that had a bad message-id. And if any mail server bounces a message send by yahoo groups, the users subscription is turned off. I don't know what to do about this problem. I have sent a message to yahoo groups about this problem. The problem would have been a lot easier to track down, it the bounce message was descriptive of the reason. I.e. 553 5.0.0 Invalid Message-ID Would not a better test be for message-id's of the format [EMAIL PROTECTED] ? My collection of spam has quite a few with message-id without a full domain name. I also noticed that I seem to have some of my spam that has a message-id of my own domain name in, so I assume that some of the mail comes in with no message-id in it at all.
