NAT different port to the same port but to different server

[ork0]

Hi,
our pfsense version is 1.2.2 (on wrap, so we can not upgrade, at the moment),

in our office LAN there are 2 server that listen on 5632 port, from inside there are no problem (obviusly)
to make it work from outside (WAN) we make 2 port forward nat rules :

5632 -> server1:5632
5633 -> server2:5632 (i think this is called port translation)

but who connect on server1 from outside have no problem, the connection to server 2 didn't work.

Am i supposed to do some sort of outbound port traslation? can you point me to something to check?
Other settings in pfsense are defaulted.

Many thanks in advance