I am encountering a problem when creating an outbound call using our PSTN Provider.

I make the call, the phone rings (PSTN) and I can hear the other party answer. They however, cannot hear me, and shortly thereafter the call drops. I ngrep'd the call and found that they are sending me 200 OK's after the call is set up, and OpenSER appears to relay those back to my EMTA. However, I never see the ACK return from my EMTA. What could cause this problem?

Inbound calls are not a problem.

Thanks,

Kw