[Mimedefang] Poll: Other MTA's
David F. Skoll
dfs at roaringpenguin.com
Tue Jun 11 15:24:05 EDT 2002
On Tue, 11 Jun 2002, Nels Lindquist wrote:
> I am, however, curious as to what kind of a framework you envision
> for this. I'm assuming there would have to be MTA-specific
> functions, depending on whether the MTA supported milter-like
> capabilities or not?
What I envision is a daemon which listens on port 25 and relays commands
to the real mail server. So you have something like this:
+-----------+ +---------+ +-----------+
| Sending |-------->| MDefang |------------>| Real SMTP |
| Relay |<--------| Daemon |<------------| Server |
+-----------+ +---------+ +-----------+
The MDefang Daemon and the Real SMTP Server may or may not reside on the
same host. Scenario:
Sender -> MDefang EHLO
MDefang -> Real Server EHLO
MDefang <- Real Server 220 foo.bar.com ESMTP
Sender <- MDefang 220 foo.bar.com ESMTP
... etc
So the daemon "listens in" on the SMTP conversation. (It can do
processing before deciding to forward a command from the sender to the
real server.) If the message is rejected, for example, it sends a
RSET instead of forwarding all the message content. Some abilities
will be lost -- there's no way to delete recipients based on message
content, for example, and any sort of IP-based blacklisting or relay
control will have to be done by the MDefang Daemon.
It might be a convenient and simple way to get MIMEDefang to work
with any mail server, though, so the tradeoffs might be worth it.
Be assured that even if I implement this, the Milter version will
still be the main one and the one with best features and support.
Regards,
David.
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