Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uakari.primate.wisc.edu!uflorida!mlb.semi.harris.com!thrush.mlb.semi.harris.com!del
From: del@thrush.mlb.semi.harris.com (Don Lewis)
Newsgroups: comp.mail.sendmail
Subject: Re: Local Configuration Error
Message-ID: <1990Oct3.032736.4108@mlb.semi.harris.com>
Date: 3 Oct 90 03:27:36 GMT
References: <6460@jhunix.HCF.JHU.EDU> <wayWTiX0BwwORNyX8k@transarc.com> <1990Sep21.161726.18266@mp.cs.niu.edu>
Sender: news@mlb.semi.harris.com
Organization: Harris Semiconductor, Melbourne FL
Lines: 40
Nntp-Posting-Host: thrush.mlb.semi.harris.com

In article <1990Sep21.161726.18266@mp.cs.niu.edu> rickert@mp.cs.niu.edu (Neil Rickert) writes:
>In article <wayWTiX0BwwORNyX8k@transarc.com> Craig_Everhart@TRANSARC.COM writes:
>   Right.  But what do you do when host A can only communicate on to its
>local network.  Perhaps it has bad networking code.  Perhaps there is a
>security concern.  However B can talk to the local network and the world.
>
>  The possible solutions (using only SMTP) are:
>
>   1.  Have two MX records for host A.  Preference 0 delivers to A, and
>       preference 10 to B.  Anyone sending email from outside the local
>       network will timeout on trying to send to A, and will (we hope)
>       then send to B from where it will be forwarded.  I claim this is
>       a poor choice, for it makes the whole Internet suffer the need to
>       first time out on the primary MX record.
>
>   2.  Have MX records for A pointing only to B (and to similarly capable
>       hosts).   Make sure sendmail doesn't declare a configuration error
>       when the best MX preference is for the local (i.e. B) host, but
>       instead looks for an A-record.  This method works very simply and
>       transparently.  Sendmail-5.64, as distributed by Berkeley already
>       does this IF there is only a single MX record, but fumbles it if there
>       are two or more MX records.  (This is what started the discussion).

This has the disadvantage that other hosts on the same local net as A
will send all their A-bound mail via host B, unless you have MX records
pointing to them as well :-(.

>   3.  [deleted]

How about:

    4.  Add a mailer flag which causes sendmail to speak SMTP to host A
	directly (look for A records only, do not look for MX records,
        do not pass GO, do not collect $200).  Host B would have a rule
	in ruleset 0 which would direct mail to A using the [TCP] mailer
	with this flag set, rather than the default [TCP] mailer.
-- 
Don "Truck" Lewis                      Harris Semiconductor
Internet:  del@mlb.semi.harris.com     PO Box 883   MS 62A-028
Phone:     (407) 729-5205              Melbourne, FL  32901