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Re: [ietf-smtp] Characteristics of Isolated (or mostly-isolated) industrial IP Networks

"John R Levine" <johnl@taugh.com> Mon, 06 January 2020 14:37 UTC

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Date: Mon, 06 Jan 2020 09:37:14 -0500
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From: John R Levine <johnl@taugh.com>
To: dcrocker@bbiw.net
Cc: ietf-smtp@ietf.org
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Subject: Re: [ietf-smtp] Characteristics of Isolated (or mostly-isolated) industrial IP Networks
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> On 1/5/2020 9:19 AM, John Levine wrote:
>> In article <3c50a793-dd26-3254-f9e3-b642793918b7@dcrocker.net> you write:
>>> What else is distinctive?
> ...
>> If it sent mail to any other address, or if the message rate was much above
>> one a minute, we'd know something was screwed up with its mail.
>
> This sounds like a variant of blocking outbound port 25.

It's exactly forcing all the mail through the submission host so it can do 
outbound filtering.  That's been common on consumer mail systems for 
decades.

Regards,
John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly

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