[Mimedefang] sending relay has no MX record?

[David F. Skoll]

On Mon, 31 Jan 2005, Lee Dilkie wrote:

> I think Gary asking something different. He wants to check if the "from"
> domain has an MX record.

If the sending domain lacks both an MX and an A record, then Sendmail
will not accpet mail from that domain unless you've enabled
FEATURE(`accept_unresolvable_domains')

AFAIK, no modern UNIX systems come with that feature enabled by default.

> I wouldn't think you'd get many hits on this sort of test, anyone who's
> gone through the trouble of setting up a domain has probably also
> defined an MX record. But let us know if you do get any hits, I'm curious.

If you're running a standard Sendmail installation, just do this:

grep 'Domain of sender address .* does not exist' /var/log/maillog

(or wherever your mail log lives.)

I get tons of these; here's an example:

Jan 20 06:20:44 www sendmail[25291]: j0KBKYsg025291:
ruleset=check_rcpt, arg1=<obscured at roaringpenguin.com>,
relay=bgm-68-175-203-192.stny.rr.com [68.175.203.192] (may be forged),
reject=553 5.1.8 <mford at roaringpenguin.com>... Domain of sender
address ENJOY-SEX- at egjukggatbvu.lt does not exist

--
David.