I can't say, but I do know that many of us toss a whole lot of mail at EHLO,
some at MAIL FROM:<> and some at DATA. The idea I was thinking about was
whether it provides any value whatsoever to at least know that you are
authentically dealing with a legitimate source sooner, without having to send
even a whole header.
Well, there's STARTTLS. Again, it's there, I believe there's pretty broad
support, but it doesn't seem popular outside of some specialized financial
environments.
Also remember CSV which Dave and I concocted to allow sites to identify
the hosts that are supposed to be mail clients.
R's,
John
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