[Mimedefang] filter_sender, authenticated or smtp (port 25) Connections

Joseph Brennan brennan at columbia.edu
Tue Feb 21 10:07:29 EST 2012

Jobst Schmalenbach <jobst at barrett.com.au> wrote:

> A number of clients (this includes thunderbird and some apple clients)
> come by default sset to 465 so I guess that is one reason why I chose
> this. The other point is that port 465 is an SSL channel with SMTP inside
> it, so right from the start on the data is encrypted.

You can require TLS at port 587, and then all the data but EHLO will
be encrypted.

The problem is that 587 is defined as a standard and 465 is not. 465
was proposed in 1997 but revoked in 1998 in favor of TLS over the
standard ports (25 or 587). 465 has since been assigned to something
else. The only client I know of that ever required 465 was Entourage,
a Microsoft product for Mac OS that was discontinued years ago.

It's sad to hear that any client today defaults to 465, fourteen
years after its use was rejected. I'm afraid it does not astonish
me at all but it is sad.

Is it time to propose 465 as a standard again?

Joseph Brennan
Columbia University Information Technology

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