[exim] using different ports for different mx preferences

Hi all,

This is a new post quoting a section of a previous post.

-snip-
Background:
The idea is to develop a config that could determine which MX record had
been used to make the initial connection (by getting the firewall to
forward the SMTP conversation to different ports on the same server,
based on the IP address the connection initially came in on).
This would avoid having to have a dedicated box and dedicated config for
each MX preference.
-snip-


I'm seeing a lot of junk-mail deliberately going for the lower
preference MX records first (by lower preference I mean MX records with
a higher numerical value than the others). The thought is to be more
strict/thorough about checking connections that are initially made to
the "wrong" MX (because I don't expect this of a "genuine" properly
configured MTA).

Is it acceptable to just dump connections that make no attempt to follow
the RFC's and go directly for the lower pref MX's. I have 5 other boxes
(in separate locations) that _should_ have been tried before anyone
would have a valid reason to connect directly to the lowest pref box.

Is anybody else already doing this?
Does it work for you?

Thanks
Jason_Meers