motty.cruz:
> 450 4.1.8 <cli...@tld.com>: Sender address rejected: Domain not found
reject_unknown_sender_domain
Reject the request when Postfix is not final destination for the
sender address, and the MAIL FROM address has no DNS A or MX
record, or when it has a malformed MX record such as a record
with a zero-length MX hostname (Postfix version 2.3 and later).
The unknown_address_reject_code parameter specifies the numeri-
cal response code for rejected requests (default: 450). The
response is always 450 in case of a temporary DNS error.
The unknown_address_tempfail_action parameter specifies the
action after a temporary DNS error (default: defer_if_permit).
