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Groups > linux.debian.user > #196276

Re: exim4 and TLS Once Again

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On Wed, May 30, 2018 at 06:22:49PM -0500, David Wright wrote:
>AIUI 587 is the standard email submission port and 465 is now
>deprecated but often still in use. I think they differ in the
>details of how they handle encrypting the session.

>From a protocol standpoint 587/tcp is identical to 25/tcp, with the 
distinction that it is designated for a end-users to submit messages for 
delivery rather than accepting mail for delivery from external mail 
relays. The expectation is that there is authentication of the 
submission, either via allowed IPs, SMTP AUTH, or some other mechanism.  
Networks can block port 25 to reduce spam originating from the network, 
but allow 587 for visitors to submit email to their provider for 
delivery. Encryption is activated with STARTTLS.

465/tcp was at one time assigned to SMTP over TLS; that is, it is an 
alway-encrypted channel like 443/tcp rather than a clear text channel 
with encryption upgrade via STARTTLS. 465/tcp has been reassigned to 
another protocol (a stupid decision, but that's water under the bridge) 
and really shouldn't be used anymore. It would be a very old or odd 
installation that supported only 465/tcp and not 587/tcp.

Mike Stone

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Thread

exim4 and TLS Once Again "Martin McCormick" <martin.m@suddenlink.net> - 2018-05-28 22:40 +0200
  Re: exim4 and TLS Once Again David Wright <deblis@lionunicorn.co.uk> - 2018-05-29 03:10 +0200
    Re: exim4 and TLS Once Again "Martin McCormick" <martin.m@suddenlink.net> - 2018-05-29 04:30 +0200
      Re: exim4 and TLS Once Again David Wright <deblis@lionunicorn.co.uk> - 2018-05-29 19:10 +0200
        Re: exim4 and TLS Once Again "Martin McCormick" <martin.m@suddenlink.net> - 2018-05-29 19:30 +0200
          Re: exim4 and TLS Once Again David Wright <deblis@lionunicorn.co.uk> - 2018-05-31 01:30 +0200
            Re: exim4 and TLS Once Again Michael Stone <mstone@debian.org> - 2018-05-31 03:00 +0200
              Re: exim4 and TLS Once Again Brian <ad44@cityscape.co.uk> - 2018-06-01 14:00 +0200
                Re: exim4 and TLS Once Again "Martin McCormick" <martin.m@suddenlink.net> - 2018-06-03 23:10 +0200
        Re: exim4 and TLS Once Again Brian <ad44@cityscape.co.uk> - 2018-06-01 18:20 +0200
          Re: exim4 and TLS Once Again Brian <ad44@cityscape.co.uk> - 2018-06-02 17:10 +0200

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