Microsoft Teams client automatically sets itself as the default chat and calling app in Office

Hello readers.  Happy New Year!  Hope you're well.

Ultra quick post today.

I noticed today that Outlook wasn't displaying presence for some people when it usually does. I checked the Skype for Business client (you know, not Teams, the other one ;) ) and I could see presence. So I found someone in Outlook that showed their presence and I moved the mouse cursor over their name to get the calling card popup.

Then I clicked the speech bubble to start an IM. Curiously, it opened Microsoft Teams instead of starting a new Skype for Business chat.

So I went one further and opened the contact card and expanded the ellipses menu to start a call.

And again, the Microsoft Teams application opened and started a call to the number. The call failed in my case since I don't have the Phone System license currently.

I didn't remember changing any associations for IM or Tel or Callto protocols, but thought I would check.  System settings -> Apps -> Default Apps - scroll down to the bottom.

Click on Set defaults by app and scroll down to Teams and click Manage

This opens the File type and protocol associations for Teams. Mine was largely set to choose a default.

I changed IM to Skype for Business and I closed and reopened Outlook. Tested again and IM still opened Teams.

I repeated with Callto and TEL and the same happened.

I remembered seeing a tick box in the Microsoft Teams client. Open Teams and click your photo and settings.

Under General, there is a tick box for Register Teams as chat app for Office.

And it was ticked. I didn't remember ticking this. I still use Skype for Business as the default for IM and calling and I use Teams for collaboration and some meetings and calling. At least for now.

I un-ticked this and restarted Outlook and tested. And low and behold, I was back to using Skype for Business for chat and calling.

A few things to think about here. 

1. Somehow, this got ticked by itself. I didn't do it.
2. Although it says default app for chat, it also means presence and calling.
3. It overrides the Windows settings for default apps by protocol

It seems I'm not alone. I posted the question on Twitter and got a reply straight away that 'loads of users reported that this got automatically ticked' and 'that none of the users were TeamsOnly'.

I do mind that this got ticked by default, but I can live with that. I would love for the controls to be more granular. For instance, tick boxes for default app for chat, calling and presence in Office.  

I would also like to know how this one tick box controls the app behavior. I also looked in the registry, by the way, and none were set to Teams. If you want to know how, check this post by @shawnharry.

Would love to know if you have any thoughts and comments. 

That's all folks.

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Thanks for reading.

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