On Thu, 30 Apr 2026 21:21:43 +0200
Michael Grimm via Postfix-users <[email protected]> wrote:

> #) Using FreeBSD's pf firewall functionality to block all traffic leaving my 
>    servers via ports 25, 465, and 587, respectively, that has not originated 
>    in a FreeBSD jail running postfix

Packets from SMTP clients tends to leave your server via ephemeral
ports allocated dynamically. If you meant to say "going to ports 25,
465, and 587" these are well known SMTP ports, but this will not stop
some process connecting to SMTP servers running on other ports.

If you control all processes on your server, this may not be an issue.
If you expose complete jails to other users, they may create tunnels to
bypass your firewall.
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