The problem arises if you send an E-mail to a non-existant user on one of our domains. If our mail server bounces the message back to you, your mail server is going to choke on it, and send it back to postmaster@one_of_our_domains.com. Then, we have to deal with your mistake. That's why many mail admins want to use this new dsn.rfc-ignorant.com test.

>If every mail server blocked null senders, the problem would probably go away.

Yes, but nobody would ever get any bounce messages. Bounce messages are there for a reason.

>According to my logs, my mail server bounces between 5 and 10 messages a day >based on null sender.

Have you checked to see how many of those are spam, and how many are bounce messages that you're making another postmaster deal with (perhaps the one that is going to block your mail server)?

Even if they are all spam, how many spams do you get per day that don't use the NULL sender? I've just gone back a bit further, and of the past 68 spams we've received, not one has used a NULL sender.

Of course, you are free to block NULL senders, just so long as you are aware of the possible consequences. If you know the drawbacks, and still want to do it, it's your choice. My goal is just to make sure that you and others are aware of the drawbacks, and why we feel it's a bad choice.

-Scott

Declude: Anti-spam and Anti-virus solutions for IMail. http://www.declude.com