At 10:23 +0200 on 04/30/2007, Frank Ellermann wrote about Re: "for"
clause on Received: header field:
> Previous standards (RFC 821, 822) did not allowed several
addresses, so is these multiple mailboxes on "for" clause
never implemented?
If it's implemented it's not better than Apparently-To, as
noted in 2821 4.4, but the Apparently-To got a "SHOULD NOT".
Why allow an in essence identical damage in the for-clause ?
While I agree that multiple addresses in the for clause for
relay-server created Receive headers is a bad idea (and a privacy
issue like the above mentioned Apparently to), this should NOT
preclude the creation of a single address for clause if the message
gets cloned for final delivery once it gets to the destination domain.
IOW: If a message arrives addressed to a(_at_)example(_dot_)com and
b(_at_)example(_dot_)com, then none of the Received headers inserted on its way
to example.com should have a for clause. OTOH, the example.com server
should be allowed, if it wants, to clone the message (so a separate
copy exists for each addressee as if the original relaying server was
set to NOT group copies to the same domain into a single Multi
Rcpt-To transmission) in which case inserting the single addressee
for is a non-issue (ie: is in the same class as if this was the only
*(_at_)example(_dot_)com address in a multi-address message). If the message is
not-cloned but just delivered to each mailbox with no changes, there
should be no for clause in the exanple.com inserted headers.