[. . .]
>  > 2) For each MX in turn, connect to port 25 (you can usually do this
>>  using a telnet program; from a command line it would probably look
>>  something like "telnet mail.example.com 25") and issue some SMTP
>>  commands to verify what's going on.
>
>I can't seem to do that -- looks like the connection attempt just times
>out, for both primary and secondary servers.  Any other ideas on this?

Some mail servers detect if your connecting to them via telnet and
drop the sessions automatically.

Another subscriber sent me private email and said that he
reconfigures his mail client so that it uses the MX as its outgoing
mail server (SMTP server).  Then he tries sending a test message to
the bouncing address.  If you're using an email client which reports
the exact error message it gets when it fails to send mail this can
work as desired.  (Of course if you use this method you run the risk
of actually sending the subscriber your test message.)

On the other hand you can also just include an excerpt from the
bounce or monitoring report and have them do their own testing.

>I also just noticed, thanks to your tip, that ALL of the errors for at
>least the last two days are for domains that are all in caps, so taht may
>be part of the issue as well.

LISTSERV automatically translates all hostnames into upper case; this
makes certain internal operations more efficient.  So the fact that
all bounces are for domains in ALL CAPS is not necessarily very
meaningful.

Thanks,
--
Jacob Haller, Technical Support
L-Soft international, Inc
http://www.lsoft.com/