There are two primary reasons a “488 Not Acceptable Here” response is seen: Unsupported Codecs and Incompatible Encryption.


If you see this error in the call logs, start by checking the codecs you are sending the connector. You can always try limit the codecs to the most common used to see if that issue resolves. PCMU and PCMA are good choices here.

By default the connector will send all codecs out from Teams to your PBX/Trunk. It can be useful to filter this to only include known good codecs.


  • The connector provides an option in the portal to filter on the Codecs. Note that this is a restrictive filter, so codecs that are missing will not be added in. When you select the codecs here you can also order them in preference, which will then be reflected in the SDP.


Codec problems: 488 Not Acceptable Here in BYE message

Example where the call dropped to "488 Not Acceptable Here" from the connector is where the DTMF was negotiated in the original Invite (SDP) and the Re-Invite(SDP) had no DTMF negotiated hence, forcing the connector to drop the call 

Invite SDP with DTMF negotiation


Re-Invite SDP without DTMF negotiation


Confirm if you expect to send and receive calls to the connector platform using media encryption. If so, enable this in the PBX/Trunk settings page: