T38 SIP Reinvites

Hello all,

I’ve installed Asterisk 1.6, and am using T.38 to send & receive faxes. This works great when I’m only routing the original call, to another device on my own asterisk system, where it is received.

The problem I’m having is that my SIP trunk provider (who supports T.38), does not accept a T.38 request right out the gate. If I have t38pt_udptl=yes under my general config in sip.conf, then as soon as I try to route the call to them, I get an error that says “unsupported media type”.

When comment out t38pt_udptl=yes, the call originates as ulaw, is sent up the SIP trunk, the provider can see this is a fax, and sends a SIP reinvite, asking to use T.38. At that point, my system then says it’s an unsupported media type!

Is there anyway to make asterisk use T.38 passthrough, but only upon seeing a reinvite? Please help! Many thanks in advance.