At 03:22 PM 6/5/03 -0400, Kee Hinckley wrote:
At 10:52 AM -0400 6/5/03, Yakov Shafranovich wrote:
The "FROM" field is the one that will get C/R checked, since that is
the mailbox that sent the email. Additionally, the "MAIL FROM"
addresses that is used in SMTP is not intended to this purpose,
rather it indicates a mailbox to which errors should be sent to. It
is perfectly legal and sometimes even recommended in RFC 2821 to use
<> for the MAIL FROM.
Are you advocating that C/R systems send mail to the From: address
rather than MAIL FROM? That strikes me as exceedingly wrong. MAIL
FROM is for notification of delivery problems--and that's exactly
what C/R is. Furthermore, we've seen on this list what happens when
a C/R system sends to From: instead of MAIL FROM--everyone who posts
to the list gets challenged by the person who forgot to whitelist the
mailing list. This is the "On Vacation" message problem all over
again.
There are basically two choices;
Envelope from a.k.a. MAIL FROM, and
Reply-To: (or From: if there's no Reply-To:)
If you view a challenge as a DSN then envelope from is the proper
choice. I'd even go so far as to format the challenge as an
RFC 1894 compliant DSN. (This has the interesting side effect
that challenging a mailing list is likely to unsubscribe you
automatically) And like any DSN, I recommend including the
message-id in the In-Reply-To: and Reference: headers.
If however, you view a challenge as a new message,
then sending it to the Reply-To: (or From: if there is no Reply-To:)
is the more logical choice.
Personally I feel that challenges are DSNs, so envelope from
is the right choice, but I can see the "new message"
point of view too.
Scott Nelson <scott(_at_)spamwolf(_dot_)com>
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