PORT_ACCESS Configuration to accecpt inbound mail from 1 IP address

Question

I have a inbound mail proxy that relays imbound mail to my final destination iMS5.2 mail server, for this reason I want to block all un-autheticated inbound connections to my iMS5.2 server except for the IP address of the mail proxy(s).
It seems the way to do this is through edits to the PORT_ACCESS mapping table.
My default looks like so
PORT_ACCESS
  *|*|*|*|* $C$|INTERNAL_IP;$3|$Y$E
  *  $YEXTERNALWhat I think will do as I require would look like this.
We do not allow users of our sub-net to send outbound mail in an unauthenticated manner, so I think these rules will not affect authenticated users.
PORT_ACCESS
  *|*|*|*|* $C$|INTERNAL_IP;$3|$Y$E
  TCP|*|25|212.115.144.233|*   $Y
  TCP|*|25|*|*              $N500$ Not$ Inbound$ MX.
! *  $YEXTERNAL Since the last rule of the origional enabled all inbound connections, the dropping of the line with the additional 2 filtering linnes should do what I want.
Thou I'm not quite sure about the meaning of the $YEXTERNAL key word line, this seems to accept from all "*" sources (accept as designated by the "$Y"), as to the meaning of the terminating "EXTERNAL" Keyword, I'm not sure of the meaning.
-Lee

Answer 1

I would set up a test box, and test. The documentation for port access is somewhat foggy to me, too . . .