On Thu, Jan 15, 2009 at 12:41:52AM -0800, Darren Pilgrim wrote:
> A while back someone posted a message about how MTAs generally respond
> to an unresponsive server given three different ways of setting up
> multiple MX mail servers:
There are really only two scenarios, the only impact of weights is on
the ordering of the hosts tried, not on the number of hosts tried or
what happens when they are tried.
Some MTAs will try multiple MAIL transactions per-delivery if some
recipients temp-fail at the first MX host. The treatment of logical
hosts vs. multiple MX records is the same as with connection retries
(see below).
Do you mean this message?
http://groups.google.com/group/list.postfix.users/msg/cf58585e240d9b8a
> 1. A single MX record with multiple A's for the hostname:
>
> example.com mail is handled by 10 a.mx.example.com
> a.mx.example.com has address 192.0.2.100
> a.mx.example.com has address 192.0.2.101
> a.mx.example.com has address 192.0.2.102
At least some Sendmail systems will try at most one connection per
delivery.
> 2. Multiple MX records with equal priority with a single A for each
> hostname:
>
> example.com mail is handled by 10 a.mx.example.com
> example.com mail is handled by 10 b.mx.example.com
> example.com mail is handled by 10 c.mx.example.com
> a.mx.example.com has address 192.0.2.100
> b.mx.example.com has address 192.0.2.101
> c.mx.example.com has address 192.0.2.102
If multiple connections are supported, most MTAs will try multiple
connections per-delivery (until one succeeds or a limit is reached).
--
Viktor.
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