Keith Moore <moore(_at_)cs(_dot_)utk(_dot_)edu> writes:
VERP isn't well-designed then. a recipient-unique envelope return address
is useful, but it's unwise to expect that every message sent to that
address is a nondelivery report - there is absolutely nothing in the mail
specifications that says that only nondelivery reports should go to that
address.
It's a fact that most user agents don't know much (if anything) about
envelope addresses, and I can't think of one which offers a "reply to
envelope address" command. Gateways from RFC 821 to other protocols
(essentially, a UNIX delivery agent is such a gateway) tend to throw
away envelope (To) addresses and keep header addresses only.
If the mailing list is for announcements only, you can add a Reply-To
header to divert messages from real people (and unfortunately, some
out-of-office notifications) to a suitable account, and the remaining
mail to the envelope from should come from an automated service.
Actually, you don't care which one--if your mailing list is so large
that you can't afford dealing with bouncing addresses manually, a lost
subscriber doesn't matter at all. ;-)
That's precisely the reason that the MAIL FROM address is exposed in the
message header as return-path - so the address can be used for automatic
responses that are generated after the message leaves the transport/delivery
system.
Ah, this is new in RFC 2821. Nice, however it doesn't seem to be
implemented widely.