At 09:35 +0200 on 06/14/2007, Arnt Gulbrandsen wrote about Re:
2821bis: received: ... for clause:
The implementations I've seen use the "for" only if there is one
address. Isn't it already constrained to one mailbox?
Sort of. Sane implementations constrain it to one mailbox. Must not
reveal bcc and so on and so forth.
I think my opinion is that since other concerns constrain it to one
mailbox and the syntax is broken except in the single-mailbox case, the
syntax should constrain it, too.
Given the single-mailbox constraint, the exposure of the address in a
for clause, should be a non-issue no matter how the address ended up
in the RCPT-TO envelope list (Address in To/Cc/Bcc or via a mailing
list subscribe) since the message is being delivered to that single
mailbox not more than one mailbox at that domain.