Thank you for your answer.

I have liberal-dtmf but the way I understand it to be working is "offer one but accept any".
In any case, it is not doing what I need, which is "accept any but do both".

ANY to me means receive either rtpevents (DTMF(RFC.2833)) **OR** sip (DTMF(INFO)).
BOTH to me means send both of the above simultaneous.

It might not make sense to outsiders but our App Server needs BOTH at the same time.
*** This is not a problem for our PROD, our carrier SIP trunk sends them BOTH simultaneously. It was our requirement.
*** This has not been a problem on DEV with our previous PBX (Cisco) which I didn't maintain but which was doing BOTH. No idea how that was configured.

I had to replace our Cisco PBX and am configuring a FS PBX on which I want this:

*** DTMF(RFC.2833) in --> DTMF (RFC.2833 + SIP INFO) out
or
*** DTMF(SIP INFO) in --> DTMF (RFC.2833 + SIP INFO) out.

Alternatively, I am looking for a SIP soft client that can do BOTH at the same time.
I have tried SjPhone, eyeBeam, Linphone and Ekiga and (as expected), they don't support BOTH at the same time.

Any help/suggestion is welcome. Thank you!
A.C.