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From: avolio@decuac.DEC.COM (Frederick M. Avolio)
Newsgroups: comp.mail.sendmail
Subject: Re: Secondary mail-router
Message-ID: <1990Aug29.122434@decuac.DEC.COM>
Date: 29 Aug 90 16:24:34 GMT
References: <5080@hemuli.tik.vtt.fi>
Sender: news@decuac.DEC.COM
Reply-To: avolio@decuac.DEC.COM (Frederick M. Avolio)
Organization: Digital Equipment Corp., Washington ULTRIX Resource Center
Lines: 6

One way to to do this, of course, is to use bind and have your relay
(in sendmail.cf) be relay.yourdomain.  Then you need to have multiple
MX records for relay.yourdomain pointing to the main and secondary
relays.  When the main is down the secondary would get it.

Fred