Hi Heiko,
On Wed, 16 Jun 2010, Heiko Schlittermann wrote:
>>> Does exim use the Backup MX if the primary MX is available? Can I
>>> configure exim to prefer the primary MX?
>>
>> Exim should try the primary first, as any MTA should. Sometimes it may
>> fail to reach the primary, and fall back to the secondary, particularly
>> if the primary uses greylisting. The secondary is tempfailing the mail,
>> because *it* thinks the primary is still up, which causes exim to try
>> the primary again later. Seems fairly normal and OK to me.
>
> But it's quite stupid by second mx, to think that my (network)
> connectivity to the second mx is the same as to the first mx.
Maybe, or maybe it just hasn't noticed yet. I implemented a trick with
exim to do exactly this, to ensure that the backup MX does not accept mail
when the primary is still up, to reduce the backup MX spam problem:
http://blog.aptivate.org/2009/01/28/backup-mail-exchangers/
I reduced the callout positive cache expiry time to five minutes, but
still during that time, the backup MX will think that the primary is still
up. I think that it doesn't do any harm except to slightly delay mail
being accepted by the backup when the primary is down.
Cheers, Chris.
--
_ ___ __ _
/ __/ / ,__(_)_ | Chris Wilson <0000 at qwirx.com> - Cambs UK |
/ (_/ ,\/ _/ /_ \ | Security/C/C++/Java/Perl/SQL/HTML Developer |
\ _/_/_/_//_/___/ | We are GNU-free your mind-and your software |
