From: Alan Becker (beckerasoftrends.com)
Date: Fri Sep 05 2003 - 12:45:34 CDT

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I went to the IANA site and pulled the "current" listing, which is
excerpted below:

---------------------------------------------------------------------------------

PORT NUMBERS

(last updated 2003-08-28)

The port numbers are divided into three ranges: the Well Known Ports,
the Registered Ports, and the Dynamic and/or Private Ports.

<snip>

kpasswd 464/tcp kpasswd

kpasswd 464/udp kpasswd
# Theodore Ts'o <tytsoMIT.EDU>
urd 465/tcp URL Rendesvous Directory for SSM
igmpv3lite 465/udp IGMP over UDP for SSM
# Toerless Eckert <eckertcisco.com>
digital-vrc 466/tcp digital-vrc
digital-vrc 466/udp digital-vrc
# Peter Higginson <higginsonmail.dec.com>

---------------------------------------------------------------------------------

I don't know what an SSM service is, but this appears to be the current
assignment
for port 465. Apparently, the Linux /etc/services listing is not quite
up-to-date
for port 465. I looked up the RFC you mentioned (thanks), and it seems
to me that
this legitimizes the use of port 587 for such purposes, so I'll probably
stick with that
port rather than 465. Thanks for your response.

If anyone else has opinions on this, the issue is still open for me. . .
A. Becker

Frederick M Avolio wrote:

> At 12:30 AM 9/5/2003 -0400, Alan Becker wrote:
>
>> Thanks so much for the information posted in the response below: it was
>> _most_ helpful.
>>
>> I have configured Postfix as described below to listen on alternate
>> ports. Currently,
>> it is listening to 24, 25, and 587. In the early stages of deploying
>> this service, we
>> have encountered 2 external connectivity providers (out of 3 tried)
>> which are
>> filtering or redirecting port 25. In both cases we were able to
>> connect using one
>> or the other of the alternate ports. Obviously, this interference
>> with port 25
>> is already a significant issue.
>> I would like to configure as large a set of alternate ports as
>> practical, while sticking
>> to ports that have some relationship to mail services. I reviewed
>> the /etc/services
>> file in RH8 to see what might there. I came up with the following:
>>
>> Port (service_name) Description
>> 24 (_none_) Private mail
>> 50 (re-mail-ck) Remote mail checking protocol
>> 174 (mailq) MAILQ
>> 587 (submission) Mail message submission
>> 465 (smtps) smtp over SSL (TLS)
>
>
>
> Use 465. It has been revoked for this purpose, but is so far unused
> and unassigned to anything else. (The TLS standards community moved
> away from assigning an additional number for every protocol that might
> want TLS.)
>
> I recommend using this one.If you *must* use other numbers (and why
> would you? That is the purpose of using assigned ports), stick to ones
> which are guaranteed to remain unassigned rather than ones that *seem*
> to be somehow associated with e-mail. Isn't it easier for your folks
> to just always use port 465? If you have to add more ports, 587 is
> also safe. It seems to me that Postfix fulfills the spirit of RFC 2476.
>
> Fred
>

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