In my postfix setup I have enabled the option
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smtpd_sender_restrictions =
check_sender_access hash:/etc/postfix/sender_access,
reject_unknown_sender_domain
This means that any mailserver that tries to deliver a mail to my system needs to have a valid domain name in the "Mail from:" header.
Sure enough, the mailserver that serves the authentication mails gives as an argument an invalid domain name, and so it's mails get rejected outright.
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Nov 11 13:51:15 sine postfix/smtpd[16302]: NOQUEUE: reject: RCPT from unknown[ipaddresshere]: 450 4.1.8 <nobody@dwagon.erfworld.com>: Sender address rejected: Domain not found; from=<nobody@dwagon.erfworld.com> to=<censored@censored.x> proto=ESMTP helo=<dwagon.erfworld.com>
Seen as how many online mailhosts use similar settings (it is one of the simplest ways to deal with bulk spam), good fixes include:
- Alter the from: header to point to a legitimate hostname (http://www.erfworld.com would work) that can be resolved normally,
- register the dwagon.erfworld.com subdomain and point it to either the website or the mailserver (preferably the mailserver).
HTH.


