From re-reading your question it sounds like you want to block traffic leaving your network so this will do that. If you want it the other way around or have additional questions please ask.
Assuming your LAN is 192.168.1.0/24 and your Exchange IP is 192.168.1.100:
access-list block_traffic_out permit ip 192.168.1.0 0.0.0.0 any eq 80 <- allows traffic from entire subnet out on port 80
access-list block_traffic_out permit ip 192.168.1.0 0.0.0.0 any eq 8080 <- allows traffic from entire subnet out on port 8080
access-list block_traffic_out permit ip host 192.168.1.100 any eq 25 <- allows traffic from Exchange out on port 25
access-list block_traffic_out deny ip 192.168.1.0 0.0.0.0 any <- denies all other traffic out of your network
Apply this access-list to your inside interface:
access-group block_traffic_out in interface inside
Since ACLs are processed from the top down you will need to add additional entries to the ACL in the order you want them processed. You should note, however, that this is an extremely rigid ACL that will kill all traffic leaving your network except if specified.
