From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@9fans.net
Subject: Re: [9fans] A question on remotemail
From: "Russ Cox" <rsc@swtch.com>
Date: Tue,  8 Jul 2008 12:52:17 -0400
In-Reply-To: <20080708150047.GG29253@hermes.my.domain>
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There are two different "From" addresses associated
with a particular mail message.  There is the RFC822
"From:" line and then there is the "MAIL FROM" return
address that is sent as part of the SMTP conversation.
(This is the address recorded in the "From " line at the
top of the Plan 9 mbox-format messages.  See thread
last month.)

The two are not always the same.  For example, this message
says it is From: <rsc@swtch.com>, but the SMTP return
address is something like 9fans+bounces+23450qc@9fans.net,
so that if a bounce comes back, it goes to the mailing list
software, which uses the last bit to determine which address
on the list is bouncing.

I would be a little surprised if your ISP is rejecting
based on the From: line rather than the SMTP return address,
but maybe spammers have driven them to that.
The /mail/box/$user/headers file sets RFC822 headers,
including the From: header.  The upas/smtp arguments set
the SMTP return address.

As for how to do it "right", editing remotemail sounds fine.
The nice thing about upas is you can understand the shell
scripts and edit them, instead of having to shoehorn
everything into some preordained config file.

Russ