[BlueOnyx:12453] Allow Inbound Email From Only One IP or Host

[David Hahn]

Hi all,
I have a blue quartz 5100 still running the old
nuonce/solarspeed av/spam package. It no longer
updates sa and clam ect... With the garbage being
sent it no longer has much of a chance protecting
mail as good as the current av/spam package does.
BTW, the current package works GREAT!

Using 2 servers one the MX points to with the av/spam
package on it (server 1 BO5601). It then scans the mail and
sends it to the BQ5100 server 2.

My question is, how do I stop mail from by-passing
the MX records and go around server 1 and directly
to server 2?

If i use iptables to block port 25 for all but
one ip address local mail, users mail admin root ect..
quits sending on server 1.

# iptables -A INPUT -s ! 1.2.3.4 -p tcp --dport 25 -j REJECT
or
# iptables -A acctin -s ! 1.2.3.4 -p tcp --dport 25 -j REJECT

What other rule would I use to keep the localhost and domains
and the internals happy on server 2 and only allow mail from
server 1 and no where else or a more permanent better way to
do so.

TIA
David