Hi, we're currently doing that for a 5000 + users. We're now at the point of fine tuning. Calls works fine, inside to outside, outside to inside (almost), but I have a very anoying thing happening to me and I have no clue what is the cause.
Here's my set-up resume: Mitel pbxs, Unify SBC, Teams office 365 infra. Got my trunk/SIP peer profile/ars route worked out, but when I was doing some testing we couldn't place call to certain cellphones providers.
In the Call routing tab of my SIP peer Profile, I setted the "Private SIP Trunk" to Yes. Since then, I can call everywhere without problem, but since the modification, I lost the ring back tone when we place a call from an device to my Teams extension. To fixed that, in the "Signaling and Header Manipulation", I changed "Require Reliable Provisional Responses on Outgoing Calls" to No and I got the ring back tone again BUT NOW instead of the extension number I see on the phone's acd screen "Private Ringing".
Look like it's a never ending series of I fixe something to create an other problem.
thanks