I'm receiving this error on plesk:
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
SMTP error from remote mail server after RCPT TO:<email@example.com>:
host mail.domain.com.au [ip-adress]:
553 sorry, that domain isn't in my list of allowed rcpthosts; no valid cert for gatewaying (#5.7.1)
firstname.lastname@example.org is setup like forvarding domain..
Thanks in advance!