I've noticed a fair number of messages list the one below in my mail logs:
Jul 20 09:52:17 mail postfix/smtpd[2352]: NOQUEUE: reject: RCPT from unknown[ww.xx.yy.zz]: 450 4.1.8 <[email protected]>: Sender address rejected: Domain not found; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<host.xxxxxxxx.com> When these messages were generated, I had reject_unknown_sender_domain included in my list of smtpd_sender_restrictions. That particular reject option is supposed to "reject sender from domain without A or MX record." Unfortunately, when I went to check on one of the domains (because a message I was expecting kept being rejected) I discovered that the IP address logged had both an MX and an A record. Except for the obvious (IP and name) the records were the same as those for systems whose mail was being accepted. EXCEPT, the MX preference value is 0 (ZERO) for the domain whose mail is being rejected. For now, I removed the reject_unknown_sender_domain setting and I'm finally receiving the expected messages, but I'd like to know if this is a known bug and if not, what I can do to help confirm it. (As you can see, I didn't put the actual names or IP addresses here, but I'll share them directly with a developer if asked.) Steve Vallière
