550-Unknown user 550 Sender verify failed

[GRR-ZA]

Hey all,

I've setup a new postal server which has been working for most outbound mail but there are a few hard fails and soft fails as per below.

550-Verification failed for [email protected] 550-Unknown user 550 Sender verify failed

450 4.1.8 [email protected]: Sender address rejected: Domain not found

What I'm struggling to understand is where it's getting the sender address from.

Any advise would be appreciated.

[willpower232]

Where are you seeing those errors, can you include a screenshot?

[bonest]

I have the same errors on the postal admin interface when sending to a domain when I use postalserver as a transactional server to send the email to a mailserver that holds the inbox for the domain.

Its kind of difficult to explain

Postfix has this explanation.

reject_unknown_sender_domain
Reject the request when Postfix is not the final destination for the sender address, and the MAIL FROM domain has 1) no DNS MX and no DNS A record, or 2) a malformed MX record such as a record with a zero-length MX hostname (Postfix version 2.3 and later).
The reply is specified with the unknown_address_reject_code parameter (default: 450), unknown_address_tempfail_action (default: defer_if_permit), or 550 (nullmx, Postfix 3.0 and later). See the respective parameter descriptions for details.

[bonest]

I found the problem. Inspired by this thread #653

It was a typo in the a Record for the rp.mail.example.com A record. I had it created as rp.mail.example.com.example.com. Fixing that A record solved my problem.