On Fri, 26 Mar 1999 16:12:37 -0500, Valdis Kletnieks <[log in to unmask]>
wrote:

>Umm.. Ben?  Maybe something is screwed up locally, but I fail to find
>an A record for listserv.opm.gov, and 2 MX entries, as follows:
>
>listserv.opm.gov.       4158    MX      10 serv1.opm.gov.
>listserv.opm.gov.       4158    MX      5 servfwDC.opm.gov.
>
>This may require major tap-dancing, assuming 'servfwDC' is supposed to
>do Listserv.  In any case, I would *really* recommend having either
>an A record or at least a CNAME to an actual A record for the listserv host.
>
Yes, I found the same 2 entries and connected with both.  In a unix installation
it is not untypical for the mail receiving machine to be sendmail running on a
different machine.  Sometimes there are firewall issues, etc which I suspect
here (given the MX host name).  I have to assume that servfwDC.opm.gov has the
appropriate instructions on how to route inbound mail to the actual LISTSERV
machine behind the firewall.  One other fairly common problem with firewall
situations is that there in an 'inside' DNS and and 'outside' DNS.  The problem
may also be that listserv.opm.gov and servfwDC.opm.gov are in the outside DNS
but not in the inside DNS and that the machine thus cannot find its name to be
able to mail out.  Maybe it needs to be called by it's internal name which is
something like QZ123.opm.gov or whatever.

It is normal and recommended for the LISTSERV machine to have an A record and it
may also have an MX record although that is not required.  SMTP when mailing
first trys an MX record, but if that is not found it will next try an A record.
If the MX record answers first however, then that will be used.