Re: Change Headers That Exchange Uses To Deliver Mail?

From: Rich Matheisen [MVP] (richnews_at_rmcons.com.NOSPAM.COM)
Date: 03/05/05 

Date: Sat, 05 Mar 2005 10:10:39 -0500

"B.Gordon" <dbgordon@sympatico.ca> wrote:

>When someone sends a BCC mail to recipients in my domain, the TO: header
>field is blank and as a result, the message is getting dumped into my
>badmail and a copy is going to the postmaster in my domain.
>
>It turns out that our ISP has some kind of SPAM filter that parses the BCC
>content

The "Bcc:" header should be removed by the transmitting e-mail system.
If that header remains with the message it's no longer useful since
its contents are disclosed.

>prior to delivery to me and places the intended recipients in a new
>header called:
>
>X-NETSCAN-TO:

So the BCC information is transmitted to the recipients? That kinda
makes it pointless since the list of recipients is exposed.

>Is there a way to tell my exchange server to use the contents of that new
>header to determine the recipients in addition to the normal TO: header
>which works the rest of the time?

SMTP mail isn't delivered using the RFC2822 message headers. The
RFC2821 command "RCPT TO" contains the recipient address.

>So, have it check TO: and X-NETSCAN-TO: to find an internal match to our
>mailboxes?
>
>I cannot get our ISP to turn off this spamguard feature and I cannot get our
>sender of this particular email to use anything other than BCC to send this
>message... So I need to configure my server to deal with this issue.
>
>Any help would be appreciated...

The original MAIL FROM and RCPT To commands should be passed to your
Exchange server if your ISP is acting only as a SMTP proxy. OTOH, if
you're having the mail delivered to a mailbox at the ISP and then
using some kludgy POP-to_SMTP contraption to read the mail from the
mailbox and resend it to your SMTP server then you really have no idea
who the original recipients of the message might be.

Given this SMTP transaction, who should get the mail, the <vendor>?

HELO
MAIL FROM:<vendor>
RCPT TO:<you>
DATA
From: <vendor>
To: <vendor>
Subject: WOW! Do we have some great deals for you!

blah, blah blah....
. 

-- 
Rich Matheisen
MCSE+I, Exchange MVP
MS Exchange FAQ at http://www.swinc.com/resource/exch_faq.htm

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