I found the following forums:
It use to work but apparently Teams made changes that require the Response packet to also include the FQDN.
I want to find out if someone is actively working on this?
that and other changes which could potentially happen in future.
There are certified SBC’s you can put into the middle between Asterisk and Teams.
Alternatively, the Kamailio and OpenSIPS communities seem to have become the free option for being the SBC.
I’ve used this guide to help me build my Kamailio SBC for Teams.
Teams needs SRTP, so ensure your Asterisk supports and uses it for this.
You can successfully work around this with RTPEngine, but why if you don’t have to.