On a compute with multiple IP addresses I wanted to pick the IP address used for outgoing smtp packets.
I tried to used action "relay" relay src 10.1.1.7 Which did set the outgoing address, but it then created a different problem. I was using a match from src 10.1.1.0/24 for any action "relay" to allow the computer on the local subnet to relay without authentication.. If the "src" option is used in the relay, the "src" in the match tests against it rather than the origin address in the incoming smtp packet Since incoming external smtp session were allowed I accidentally created an open relay.
