Bug#308323: exim4-daemon-heavy: sometimes splits mail between alternative MXs for no good reason

[Marc Haber]

On Mon, May 09, 2005 at 02:49:37PM +0200, Steinar H. Gunderson wrote:
> We're currently running Exim on a quite bandwidth-constrained links, and
> the following has become a problem lately, especially with aliases etc.
> in the loop:
> 
> Sometimes, when an alias expands to multiple addresses that point to the
> same domain (which has multiple MX records), Exim chooses to deliver
> to half of the recipients via one MX and the other half to the other MX.
> Thus, the message is sent out twice on the link, instead of simply
> adding more RCPT records to the already existing connection. This
> appears quite random to me; what should happen is that Exim decides MX
> for a domain only once during delivery of a given message, instead of
> forking into two processes delivering the same message.

I suspect the following behavior: Whenever a new message is generated,
a delivery process is usually forked immediately which delivers the
message. This might be your behavior here.

A possible remedy would be to run exim in queue-only mode and to have
a queue runner invoked on a regular basis. There are options which
make exim route first and deliver later which possibly does the best
job in grouping together deliveries.

This is, however, a configuration highly special to your case and not
suitable to be the default.

That being said, I would be interested in logs.

This bug will be closed by the end of may if I am not convinced by
then that it is really a bug in exim.

Greetings
Marc

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