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Re: exim as backup mx

On Thu, Oct 23, 2003 at 07:23:13AM -0700, moseley@hank.org wrote:
> On Thu, Oct 23, 2003 at 01:37:27PM +0100, Antony Gelberg wrote:
> > Hi all,
> > 
> > I'd like to set up exim as a backup MX for a friend's domain.  Any tips on
> > doing this?  I was going to put the domain in local_domains in exim.conf,
> > and have a catchall in /etc/aliases.  But how do I forward the queued
> > mail to his server when it comes back up?
> I'm glad you asked, because I have been wondering about this, too.
> I use "relay_domains" for the secondary, and it's what is suggested at
> http://sysadmin.oreilly.com/news/exim_0701.html.  I'm not sure if 
> there's a better way.
> The problem I find with that is normal checks (like what are valid 
> users) are not done.  So when some spammer connects to the main server 
> they may get rejected at the rcpt to: line, but on the secondary they 
> are not rejected.
> I also once set up a "secondary" to be exactly like the primary and 
> then used aliases to forward mail to the main.
> Unless dealing with a large amount of mail I wonder if it's even worth 
> using a secondary.  The only reason for it would be to read your mail if 
> you primary machine fails.  For example, for a small home setup if your  
> local mail server is down it probably means everything is down, so 
> you can't access the secondary anyway.  On my home setup I find that the 
> only mail that goes through the secondary is spam.

I guess the rationale is that his main server is behind an ADSL
connection, as he has more control that way.  However, if the connection
or server goes down, he doesn't want incoming mail to bounce.

The link you provided states:
: Once you've done this, your host will accept mail from outside that is
: addressed to those domains, and will relay it according to your delivery
: configuration.

So...  I guess it depends on the "delivery configuration".  I wouldn't
want it to attempt immediate relaying, as the main server would probably
still be down, and it defeats the object.


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