Inband DTMF and Voicemail

[david]

I have a SPA3000 that I use with several different services. So far the most consistent method of DTMF for all of them has been Inband. There are 2 services that seem especially picky, though: Voxalot and voipmich (for toll-free calls).

Aside from DTMF Tx Method (set to Inband), the SPA3000 also has a "DTMF Process AVT" setting (default is Yes). If it's set to No, the AVT (RFC2833) payload type will not be included in outbound SDP. It seems reasonable to me (though I'm no expert) to keep it set to Yes even if using Inband DTMF, in order to process incoming RFC2833 signals.

However, Voxalot voicemail will not recognize Inband DTMF unless DTMF Process AVT is set to No. If it's set to Yes, Inband will work fine, though.

Voipmich on the other hand, is just the opposite. If DTMF Process AVT is set to No, DTMF is not recognized. It must be set to Yes.

I haven't found any other services that care one way or the other.

Do you think it might be possible to get the Voxalot voicemail system to recognize Inband DTMF even when AVT/RFC2833 is included in the outbound SDP?