Registering SMTPS again would only provide short-term relief
(providers would soon block it as well) at the cost of creating
standards confusion.
Exactly right. SMTPS really is a solution to a very different
problem, one that cannot be leveraged as a solution to the problem
you describe except in, as you say, the short term.
Actually, I think this might argue *in favor* of registering 465.
Right now, 465 is used for unauthenticated encrypted submission. We
don't want people using unauthenticated encrypted submission; we want
them using authenticated submission, either on port 25 or on port
587. As a matter of fact, open 465 ports mean that, for example,
spammers will have a new way to get through firewalls and spam. (And
I would not be at all shocked if there were installed SMTP
implementations with SSL-SMTP listening on port 465 without their ops
knowing about it.) Maybe 465 should be registered to, in effect,
encourage people to make sure it is turned off.
the problem is that port registration conveys so little information,
and it invites people to make incorrect inferences.
maybe what we need is an RFC titled
"use of TLS or SSL with separate ports considered harmful"
or
"use of port 465 with SMTP and SSL considered harmful"
Keith