[gtaSAGE-members] Secondary MXs and Spam policies.

[Fraser Campbell]

On September 17, 2004 10:00 am, Adrian Chung wrote:

> Well, I've been wondering where the justification in having a
> secondary MX even is these days.  If most MTA's are well-behaved
> enough to retry for a reasonable period of time against a domain with

There's not much you can do about some MTAs.  We had a supplier whose email to 
us bounced, we had a secondary MX and our DNS was definitely available, it 
should not have bounced.

It bounced the message immediately because it could not reach the primary MX.  
I never bothered finding out what MTA they were running.  Most MTAs could be 
configured to behave this way, so it was probably just a case of clueless 
admining.

> one MX record pointing to a server that's temporarily unreachable, why
> even bother having a secondary (or secondaries) that aren't just spam
> traps?

One case where secondary MX definitely makes sense is when you have multiple 
Internet connections.  We have quite a few customers in this scenario, 
primary MX goes down, secondary MX is hosted on the other connection and 
receives the email.  Primary and secondary can be different machines or even 
the same machine, either way they are aware of their local connection and can 
relay directly to each other, resulting in almost immediate mail delivery 
from the Internet even when the primary is unreachable.

I would not use a secondary MX that is under someone else's control.

If the secondary is not hosted on an alternate local Internet connection then 
I don't think I'd bother with it then either.  Why queue mail on your own 
hardware if you're not going to get it any faster, your senders have MTAs 
that should queue it anyway?

-- 
Fraser Campbell <fraser at wehave.net>                 http://www.wehave.net/
Georgetown, Ontario, Canada                               Debian GNU/Linux