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

2020-01-06 08:37:31
On 1/5/2020 9:19 AM, John Levine wrote:
In article <3c50a793-dd26-3254-f9e3-b642793918b7(_at_)dcrocker(_dot_)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(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly

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