On 2021-04-29 Colin Stanners wrote:
I'm afraid that if I understand the situation correctly, the MXVerify
result is not an non-error, it is a real problem, and the likely
cause of your issue.

See the Gilbert reply.  This doesn't jive with the understanding of
these 2 old hands.

That serverfault link is unrelated, you are not sending emails only,
this discussion is about your domain receiving email.

Ya, but its answer re: RFC5321 is correct:

2.3.5.  Domain Names
   Only resolvable, fully-qualified domain names (FQDNs) are permitted
   when domain names are used in SMTP.  In other words, names that can
   be resolved to MX RRs or address (i.e., A or AAAA) RRs (as discussed
   in Section 5) are permitted, as are CNAME RRs whose targets can be
   resolved, in turn, to MX or address RRs.
So per RFC is the receiving domain can either resolve to MX, *or*
direct A RR (as my domain did).

Further:

5.1. Locating the Target Host
   If an empty list of MXs is returned,
   the address is treated as if it was associated with an implicit MX
   RR, with a preference of 0, pointing to that host.
As far as I can tell, 5321 is still in force and not superseded.

I had a valid, empty (non-existent) MX record set.  That should be
valid.

If you have a different understanding, feel free to RFC-enlighten us!
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