[HELP] Outbound proxy settings

Hi,
Does anybody knows how to set an oubound proxy in *?
My * server is behind a NAT and I noticed that there are no problems with connection when I make an outbound calls using an XLite directly set to my VoIP provider. When I make an outbound call through my * server I cannot hear anything but the connection is established. I found that the only thing I set additionaly making direct calls from the softphone is “Out Bound Proxy”. How to set this in the * trunk configuration?

My current sip.conf:

register=48413103648:passwd@sip.actio.pl/48413103648

[actiotrunk]
username=48413103648
type=peer
secret=passwd
insecure=very
host=sip.actio.pl

[48413103648]
type=user
secret=passwd
fromuser=48413103648
context=from-pstn

Thanks in advance