If you have OWA with SSL, add port 443 to that.
You will need a static to point to your inside server as well.
static (inside,outside) tcp ExternalIP 80 InternalIP 80 netmask 255.255.255.255
static (inside,outside) tcp ExternalIP 443 InternalIP 443 netmask 255.255.255.255
access-list outside_in permit tcp any ExternalIP eq 443
access-list outside_in permit tcp any ExternalIP eq 80
access-group outside_in in insterface outside
With this you can also setup RPC via HTTPS without any changes to the firewall.
Brent
Systems Engineer / Consultant
CCNP, CCSP