[Asrg] 7.b. Mail administrators

[Hein Roehrig <hein@acm.org>]

I have a question about best practices regarding egress filtering on
organizational networks.

Port 25 makes sense to prevent "owned" machines from being used as
relays.

What about the other ports? I would be particularly curious about BCP
for ports 465 (ssmtp, SSL-wrapped SMTP) and 587 (submission, often
used for plain-text SMTP with an immediate STARTTLS required).

Can a case be made for spam reduction by blocking the ports for
outgoing connections? Are there many systems around that accept
incoming mail on these ports?

Of course, in an open environment there are significant advantages to
leave those ports open for roaming users and guests to connect to
their "home" mail servers for outgoing mail.

TIA,
Hein

-- 
http://hein.roehrig.name


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