Hello everyone:

we recently installed a Zultys MX-250 VoIP system. It works great
internally, but I'm having trouble with using it from the outside.

- The phone switch is behind the BM server, uses a private IP address
and has a static NAT entry on the BM server.
- I can connect to the phone switch from the Internet using the software
VoIP client. I can see other user's presence, I can instant message with
them and I can make and receive calls. Here's the problem:

I can hear what the other person says, but they cannot hear me.

I have unloaded the filter exceptions, so that cannot be the cause of
the problem. I have tried this with the client also using NAT and with
the client using a public IP address.

Any ideas? Is NAT the culprit? If so: why? And how do I get this to work?

Thanks in advance for everyone's help!