Host without a valid MX still seems to receive mail. How?

Question

One of our clients owns the domain some-domain.org.

This domain is not maintained by us, and I am wondering if I am overlooking something: our client has a forwarder setup for this domain (IE. info@some-domain.org forwards to client@someisp.com).

When I do an MX lookup on this domain I see the following:

;; QUESTION SECTION:
;some-domain.org.   IN      MX

;; ANSWER SECTION:
some-domain.org. 9264 IN    MX      50 mail.some-domain.org.

Which indicates there has been an MX-entry setup. However, this specific entry does not seem to resolve:

;; QUESTION SECTION:
;mail.some-domain.org. IN   A

;; AUTHORITY SECTION:
some-domain.org. 2359 IN    SOA     ns1.hans.hosteurope.de. hostmaster.some-domain.org. 2010062314 16384 2048 1048576 2560

But yet, the forwarder works.

Am I overlooking something? How can this forwarder work, even though this domain does not seem to have a valid MX entry?

Answer 1

If MX records are not present the delivery falls back to the A record.