Not sure what you (really) need/want but I'm sure there is some "problem in wording" here ...
Assuming Jabber does run on the 6.x SME itself:
...else you need to forward and nothing but forward
_Outgoing_ ports for Jabber will be opened automatically.
_Incoming_ ports from outside via SME 6.x *to* Jabber should/need to be forwarded, not "opened" on the server - try the option you find in the panel .-)
Make sure that you forward TCP and UDP if needed !!!
Regards