Re: Fall over mail server

From: Glynn Clements (glynn@sensei.co.uk)
Date: Fri Jan 28 2000 - 05:23:45 EST


Roy Kerwood wrote:

> I've setup a "secondary e-mail server, it is in the dns db files and set
> with no rcphosts, how will the mail that is deliverd to it get picked up can
> you point me to a howto of faq that talks about backup mail servers.

The sendmail issues are discussed in the bat book; the DNS issues are
in "DNS and BIND".

> Here is what I think I know
> 1) In theory the backup mail server comes online and becomes effective after
> the primary mail server has gone down or is no longer excepting incoming
> mail. At that point secondary mail server becomes a receive only mail
> server, by that I mean it receives the mail but does not try to forward it
> to any recipients. That way mail is delivered, as far as the sender's
> concern, but is not sent on to be individual mailboxes of the proposed
> recipient. Again in theory as soon as the primary mail server is brought
> back online and the mail is retrieved from the backup and delivered to the
> recipients.

A backup mail server will always accept mail for the domain. However,
clients will only attempt to use it if they are unable to send the
message to the primary (lowest MX) mail server.

A backup mail server will always attempt to forward messages to the
primary mail server. However, if the primary is down, it won't
succeed.

> 2) Changes to the db.files
> The db. Files contain the DNS information for our hosted sites..
> cityxpress.com. IN SOA ns1.wtsearch.net. netadmin.cityxpress.com. (
> 2000011701 ;
> 10800 ;
> 3600 ;
> 604800 ;
> 86400 ) ;
> cityxpress.com. IN NS ns1.wtsearch.net.
> cityxpress.com. IN NS ns2.wtsearch.net.
> cityxpress.com. IN MX 10 string.cityxpress.com.
> cityxpress.com IN MX 20 symmerty.cityxpress.com --- secondary mail

There should be a dot after the domain name.

Note that the backup server will probably need to be told that it is
supposed to accept mail for the domain (via the relay-domains file for
sendmail 8.9.*).

-- 
Glynn Clements <glynn@sensei.co.uk>

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