Date: Sun, 22 Apr 2001 11:57:30 +0200 (CEST) From: Paul Herman <pherman@frenchfries.net> To: =?iso-8859-1?q?Keith=20Spencer?= <bsd2000au@yahoo.com.au> Cc: <freeBSD-questions@FreeBSD.ORG> Subject: Re: about how mail routing works Message-ID: <Pine.BSF.4.33.0104221140080.88695-100000@husten.security.at12.de> In-Reply-To: <20010421114232.93992.qmail@web12002.mail.yahoo.com>
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On Sat, 21 Apr 2001, Keith Spencer wrote:
> I was wondering about m entries in dns tables. I know I can label
> several mail server entries in order of primacy smallest to
> largest number so if a machine is down the next m entry mail
> server will hold the mail for the primary, temporarily off-line
> machine. How on earth does this work?
There's really only two things you need to do: setup the 2nd mail
server, and then update your DNS Zone.
First, you need to setup the secondary mail server, so that it will
relay mails to the primary. With sendmail, this means puting the
following line into /etc/mail/mailertable:
your-domain.com smtp:[primary.mail.server.com]
This tells it to send all "@your-domain.com" mails to the primary
server (The [] brackets mean that the mail should be directly sent to
the primary mail server, ignoring any DNS MX records.) The secondary
mail server should also be setup to RELAY your-domain.com.
Before you update your DNS records, you can test your secondary server
by sending mail from there or telneting directly to port 25 and seeing
if it will relay mail to your primary server.
If that works, you just have to update your DNS zone with a second MX
entry, like:
your-domain.com. MX 10 primary.mail.server.com.
your-domain.com. MX 20 secondary.mail.server.com.
The "10" and "20" are preferences -- the lower the number, the more
prefered, i.e. other mail servers will try the primary first.
-Paul.
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