I just don't use subaddressing anywhere,
What exactly is the problem? Are you having trouble receiving messages?
Are you having trouble sending messages? Many other people use
subaddresses without trouble.
You've told us that one of your ISPs doesn't support subaddressing. Has
it occurred to you that mail receipt isn't free? Some ISPs charge for
subaddresses; some of them don't have appropriate software. Some ISPs
won't give you _any_ addresses. If you don't like that, use a different
ISP. Where is the interoperability problem?
You've told us that your two other ISPs use different subaddressing
systems. So what? Why should they match? Different domains have
different address spaces. Where is the interoperability problem?
I am interested in how the submission agent that comes with my Mac MUA
interfaces with the MTA and LDA on the Win/NT host that's my ISP's IMAP
server.
What are you talking about? Submission agents don't talk to LDAs, or to
IMAP servers. Your MUA probably doesn't even include a submission agent;
instead it uses SMTP (incorrectly, but by bilateral agreement) to relay
what you typed to a submission agent on the server.
---Dan
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