Yahoo Qmail Daemon and Mailman
My server’s mailman (or postfix) installation is mysteriously rejecting mail from one Yahoo! mail user. I don’t get it:
Hi. This is the qmail-send program at yahoo.com. I'm afraid I wasn't able to deliver your message to the following addresses. This is a permanent error; I've given up. Sorry it didn't work out. : 72.1.169.10 does not like recipient. Remote host said: 550 : Recipient address rejected: undeliverable address: unknown user: "[list name]" Giving up on 72.1.169.10.
72.1.169.10 is, in fact, the IP address of my server. [list name] is (in the real version) the real live name of the list. The list seems to work for everyone else. And it’s certainly not true that I, or my server, doesn’t like this recipient (or sender).
Aside from this anomalous behavior, it’s also funny that Yahoo! provides plain old unfiltered qmail bounce messages to its users. Wouldn’t you think a fully matured webmail service like Yahoo! would, by this point, have somewhat customized their mail error reporting messages? In fact, wouldn’t you think they would want to hide the fact that the use qmail at all, if only for security purposes? Couldn’t they hire an intern to write a few replacement error messages? Maybe I’m missing something.
A propos, I discovered this nice piece from McSweeney’s, entitled YAHOO’S MAILER-DAEMON AUTOMATED REPLY FOR FAILED E-MAIL DELIVERY IS GETTING A LITTLE TOO INTIMATE.
Update 5/30/06: Figured it out. Oddly, Yahoo! was looking up the CNAME DNS record for the domain name and replacing that in the mail header. While the original email went to e.g., listname@lists.mydomain.com, the message as delivered was addressed to listname@servername.mydomain.com. Because only lists.mydomain.com processed email for lists, the message bounced. The solution was to change lists.mydomain.com from being a CNAME entry to its own A entry with the IP address specified directly. That fixed the problem. I’ve never seen any other mail service work this way — gmail certainly doesn’t.