As I said, it's inconvenience.
_What_ is inconvenient?
Chris's proposed mailing-list rule, though dangerously naive, at least
made it obvious what problem he was worried about. Your proposal is so
vague that I have no idea what it's supposed to accomplish.
The interoperability problem is that the software on my Mac has to
support both schemes.
What for?
I know people using subaddresses with a variety of MUAs. The MUAs all
deal with incoming _mailboxes_, not incoming addresses. Why should an
MUA care which addresses are owned by the user?
Why don't you skip the vague generalities and give some specific
examples?
Yes or no: Are you having trouble sending messages? If yes, what is an
example of a message that you wanted to send? How did the system stop
you from sending that message?
Yes or no: Are you having trouble receiving messages? If yes, what is an
example of a message that you wanted to receive? How did the system stop
you from receiving that message?
No, but if I'm going to put the right thing in my Reply-To or From header,
I need to know what format the MTA and LDA are willing to accept when my
recipients send mail back to me.
Huh?
The sysadmin gives the user an e-mail address. The user types it into
his MUA. Millions of users have successfully accomplished this feat.
Why should the MUA care about internal structure in the user's address?
All it does is copy the address.
That's true, but the server (also incorrectly but by bilateral agreement)
doesn't have a submission agent either.
False. The server (most commonly sendmail; sometimes qmail with
qmail-inject) includes a submission agent.
Have you already forgotten what ``submission agent'' means? I said two
days ago what submission agents do.
I simply adopted your terminology
because you refused to discuss the real-world situation of MUAs talking
directly to MTAs.
False. The real-world situation is that MUAs talk to submission agents.
Many MTAs do not provide submission services by default. When MUAs talk
to those MTAs directly, malformed messages escape onto the Internet. In
some cases recipients can't respond since the From field is unqualified.
This problem is, as I said, solved by bilateral agreement: the MTA is
configured to provide submission services for certain IP addresses.
sendmail includes both a submission agent and an MTA, and currently
treats every message as a submission, but sendmail's author has been
adding options to change this.
---Dan
Set up a new mailing list in a single command. http://pobox.com/~djb/ezmlm.html