[Mailman-Users] MX lookup failures blocking queue

William R. Dickson wrd at awenet.com
Thu Aug 2 21:31:15 CEST 2001

On Thu, 2 Aug 2001, J C Lawrence wrote:

> > Hi all, There seems to be a little DNS weirdness going on today --
> > a couple domains used by subscribers to my list can't be looked
> > up.  Their local nameservers are timing out, so mailman is logging
> > errors like so:
> >      Can not check MX records for recipient host
> This is an MTA configuration problem, not a Mailman problem.  You
> have your MTA configured to do DNS lookups on receipt of messages.
> That is both the source of the message and the source of the problem
> (Mailman is merely repeating it into its logs).

Based on my logs and a test, it appears to be happening when the messages
are being sent, not when they're received.  And indeed, I would expect
sendmail to do a DNS lookup on the MX host of the recipient's domain;
otherwise, it wouldn't know where to send the message.  (I'm by no means a
sendmail expert, so if I'm mistaken about that, please tell me.)  So, yes,
it's sendmail that's having trouble looking up the destination address,
not mailman.

Here's what surprises me, though.  If I send mail directly to one of the
bad addresses and one of the good addresses, just using mail -v so I can
see what's going on, the message is queued to the bad address for retrying
later, and the message is delivered to the good address.  But when mailman
tries to deliver a message to a list of addresses, one of which is bad, it
doesn't deliver to anybody -- it simply leaves the message in qfiles.


 William R. Dickson -- Consuming the Earth's limited resources since 1968
 wrd at awenet.com                              http://www.manoutoftime.org/

  Professor: Hey! Unless this a nude love in, get the hell off my property.
Tresspasser: You can't OWN property, man.
  Professor: I can.  But that's because I'M not a penniless hippie."

                                                   - Futurama

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