First of all end-users would not care much what protocol it is when
"you've got mail" pops up.
And for designers, programmers, and quicker implementation its quite a bit
better if new protocol and old one share certain components. For example
MIME encoding/decoding, etc. It would faciliate process if protocol can
be implemented on same mail server software that would be able to decide
based on certain dns or other parameters what protocol to use when sending
email to the other end.
And look at the example of IPv4 vs IPv6 - IPv6. While there are substantial
improvements in features available with IPv6, as far as implementation and
design and application programmings, its not that different.
On Sun, 25 Jan 2004, Keith Moore wrote:
I'm all for separating the envelope from the message content, but I'd
be interested in investigating an even more radical change - (probably)
scrapping SMTP entirely or (less likely) branching out of the SMTP
state machine very early. Or in other words, I could see making the
new protocol similar enough to SMTP that a single server could
implement both, but that might just invite confusion.