(Off-topic for most, but some here should be able to help)
 
I know this is probably a RTFM (RTFRFC?) question, but so far I have
only found bits and pieces of the answer and not a composite solution;
hopefully someone can summarize for me...
 
We are trying to setup an "alternate" mail host for our primary mail
servers so that when one goes down, mail can be delivered to another to
avoid mail bounces (undeliverable after xx hours/days) to be queued for
the affected host.  The obvious method is a prioritized list of MX
records for the covered hosts.
 
I tried this once between two hosts and ended up with a forwarding loop
so I'm a bit hesitant to experiment by trial and error.
 
The basic question is this:  if we have DNS setup like
   hosta.foo.edu  MX   0 hosta.foo.edu
                  MX  10 hostb.foo.edu
   hostb.foo.edu  MX   0 hostb.foo.edu
                  MX  10 hosta.foo.edu
 
It's clear how "the world" sees this and treats these entries, but what
about hosta and hostb?  If hostb receives mail for hosta, will it follow
the MX chain and resend to itself?  Is this a default MTA behavior or
does it require some tweaking of the MTA?  If the latter (and the reason
for this message being cross-posted) how is this conveyed to sendmail
(Solaris), LSMTP (NT), and/or NetMail (MPE/iX)?
 
Reply directly unless the reply is relevant to the list.  Thanks in
advance...
 
Jeff Kell <[log in to unmask]>