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Re: how to match Bcc?

2003-11-11 11:41:16
At 12:35 2003-11-11 -0500, Birl wrote:

Alright, I understand that.  However, if the 'list' is an email alias, is
it really a bcc?  I guess the answer doesnt matter much as this is going
off topic.

Excepting how the ORIGINATING mail server sees the message submission, there is absolutely no difference in how the message is passed off to the recipient mail servers.

IF THE ADDRESS DOES NOT APPEAR IN THE TO: OR CC: FIELDS ON THE COPY WHICH YOU RECEIVE, THE MESSAGE IS QUITE OBVIOUSLY ADDRESSED TO YOU IN THE BLIND.

Excepting for mailing lists where each individual recipient is mailed out to, with THEIR address in the To: field (more like an old fashioned "mail merge"), mailing lists / mail aliases deliver as Bcc, whether you think the original message had a Bcc: header or not.

MOST mailing lists can be identified from some additional headers they stuff in the message. However if someone simply does (and this IS oversimplified):

:0
* ^To:.*someaddress
! addr1,addr2,addr3

each of the recipients will receive a message devoid of anything which specifically identifies them or a "list-like" (re-)sender. THe original delivery mechanism here didn't insert a Bcc: line, but rather invoked the MTA with the addresses provided on the commandline, which are taken as explicit recipients (AND the message IS NOT delivered to the addresses seen in the headers, which are just for show).

I could for instance, compose a message which says it's being delivered to your boss and to you, and discuss some really rotten secret about your personal life which you'd rather your boss didn't know about right now, but sending it like so:

        sendmail youraddress < messagefile

Will deliver it just to you. YOU would see your boss' address in the To: field and have a fit, possibly sending him a followup apologizing that he had to hear the news about you, BOTH of his daughters, and what you did with them at the company winter retreat this way... and therefore telling him yourself (or by overquoting the message which you THOUGHT he'd already received), because he never really was a recipient of the message.

Moral: don't trust headers. In the end, you received the message, and that means apparently you were addressed - if not visibly, then obviously in the blind.

To the MTA, headers are actually just a part of the message body - while the MTA adds some stuff (Received: for instance), and may check a field or two for validity (existing Date and Message-ID, domain in From:, etc), it rarely takes action on any of the data (short of deliberatley written filters).

---
 Sean B. Straw / Professional Software Engineering

 Procmail disclaimer: <http://www.professional.org/procmail/disclaimer.html>
 Please DO NOT carbon me on list replies.  I'll get my copy from the list.


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