Forwarding the fax to external number


Can i forwarding the fax to external number without install any fax module?

This is because we have the third party services provider to make the fax to email. We just forward the fax is ok.

But I get the problem is the “fax call” can not forward sometime.
The call will drop when the fax doing “negotiate” handshake tone.

The voice call forwarding even internal or external is 100% work without any problem.

Is it something module I need to install or enable something if doing fax forward?


You didn’t say what kind of trunks, if it is an IP trunk, it’s not going to work well. If you are using TDM trunks (POTS lines or ISDN) it should work fine.

sorry, We use IP trunk (SIP trunk).

May I know,
"if it is an IP trunk, it’s not going to work well"
is it means the IP trunk can not support the fax forwarding? or not stable?

It doesn’t support it in any fashion you will find useful.

If your provider supports t.38 fax over IP you can setup Asterisk as a t.38 relay and pass the call to a t.38 ATA. As far as grabbing another trunk and forward it. The is not going to work well.

If you just want to forward an inbound DID to an external number, create a custom extension with this in the dial string:

LOCAL/[email protected]

Replace the 12223334444 number with your external fax service number and make sure to create the inbound route for your forwarded fax DID.

We do the same thing to allow users to extension dial between offices.