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Article: 311
From: Anthony Howe
Date: 2005-01-25 01:54:35 -0500
Subject: Re: milter-ahead on a backup mx

Removal...........: milters-request@milter.info?subject=remove
More information..: http://www.milter.info/#Support

Erik Hensema wrote:

> Hi,
> I succesfully installed milter-ahead on our mail virusscanner/spamfilter
> server which acts as a gateway to multiple shared webhosting servers. Works
> great!
> Now I want to install milter-ahead on our backup MX, but I was thinking to
> alter the behaviour a bit: when the backup MX succesfully makes an SMTP
> connection to the downstream server, the backup MX should reject the
> connection with a 4xx temporary error. This is because when the backup MX
> can make a connection to the primary, the client should also be able to do
> so.

(I'm posting this suggesting to the [milters] list for feedback.)

Interesting twist. You are right of course that if the primary is up 
that by definition of how MX servers are to be used that the client 
should be contacting them always unless. Most spammers abuse secondary 
MXes in an effort to slip past spam filters.

My only concern is some primary MXes temporary reject a message, using 
grey-listing, or simply busy. Some poorly written clients then try the 
secondary immediately (most likely spamware) or queue the message to 
retry later on the secondary.

 > ... (suggested patch removed) ...

> Do you think this would work?

I'll have to review the code and/or write my own update based on this 
idea.  I might create a new option -B as a variant of -b. At least then 
people could experiment with behaviour.

Anthony C Howe                                 +33 6 11 89 73 78
http://www.snert.com/       ICQ:
7116561         AIM: Sir Wumpus

            "Once...we were here."  - Last of The Mohicans

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