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Article: 166
From: Anthony Howe
Date: 2004-10-18 11:58:06 -0400
Subject: Re: How Can I get around this?

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

Upwood, Jim wrote:

> This Mainframe is sending e-mail with the from as this:
> 
> @LBDRSCS.LBDCVM.STATE.NY.US:VMMAIL@LBDC.STATE.NY.US

OK. I've found the syntax in the RFC 2821 grammar:

	http://www.rfc-ignorant.org/rfcs/rfc2821.php#section4.1.2

Looking at `Path' and `A-d-l', it does appear valid and that I've 
overlook it (believing it to be obsecure rare cases). Its actually a 
form of routed address syntax. Looking at the Bat Book:

	<@A,@B,@C:user@D>

Would imply send mail to A, then A will relay to B, B to C, and C 
handles final hop to D. This is similar to:

	user%D%C%B@A

Both are forms of relaying syntax, similar to the old bang-paths. I can 
certainly parse it, BUT for certain milters like milter-sender, it might 
be impossible to perform a call-back directly to VMMAIL@LBDC.STATE.NY.US 
as it might be "guarded" by LBDRSCS.LBDCVM.STATE.NY.US.

The question I have to deal with is for milter-sender is: Do I try and 
call-back on the ultimate destination, knowing it will fail and fallback 
on grey listing, or do I connect to LBDRSCS.LBDCVM.STATE.NY.US and test 
if VMMAIL@LBDC.STATE.NY.US is accepted? Imagine a spammer that says:

	MAIL FROM:<@spam.biz:bogus@bogus.com>

Instead of doing the MX lookup on `bogus.com', I'm suppose to do it on 
`spam.biz'. Essentially you are being directed to call-back to a machine 
probably setup to say "yes" to all queries.

-- 
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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