Teams Calendar Button missing - exchange 2010 + Exchange 2016 hybrid on-prem

Occasional Contributor

Hello Tech community,


As you can see in the object, I have one Exchange 2010 sp3 RU22 and one Exchange 2016 CU12  (same forest).

The 2016 is my hybrid server, all mailboxes are hosted on Exchange 2010 db.

My hybrid seems to be well configured, no error messages at the end of the HCW, Oauth is working as expected too, I properly migrated test mailboxes.


My question is, in this scenario, is that possible to leave mailboxes on Exchange 2010 db and have the calendar button appears in Teams ?
Moreover, I tried to move a mailbox from 2010 db to 2016 db, and the calendar button is still missing.

I receive the following error in Teams logs:

"2020-04-07T09:39:48.138Z Inf UserAppsStore: Skipped calendar app with isFirstParty as true. isMailboxDiscoverable: false"


Thanks for your help



9 Replies
I think the scenario you have over the table is not supported and you might need to migrate your mailboxes from Exchange 2010 to Exchange 2016

Thank you for replying @Juan Carlos González Martín 


None of the Microsoft article states clearly that Exchange 2016 cu3 + lower Exchange version are not supported for Teams calendar button. For exemple  the Teams/Exchange interaction article says:


Users with mailboxes hosted on-premises must be synchronized to Azure Active Directory. They can make use of all the features in the above scenario, but additionally they can also change the user profile picture (if the Outlook on the web mailbox policy allows them to do so), and manage meetings, providing Exchange Server 2016 (Cumulative Update 3), or later, is running on-premises.


And I tried with an exchange 2016 hosted mailbox, the issue is similar.

I opened a Ticket, I will see what Microsoft says about this config


@Rigs33 curious if you have any more information about if the calendar app will be available is you have EX2010 + EX2016hybrid and switch CAS to EX2016 but still mbx reside on EX2010 ?

CAS and mbx still resides on EX2010, the case has been escalated to Microsoft on-prem experts.
I'm waitng for their feedback.
FYI, if i create a mbx directly on 2016 db, the calendar button appears in teams.
If I move a mbx from 2010 db to 2016 db, the calendar button is missing.
@riggs33 i just tested today myself. Mbx on 2016 has the calendar app in teams. Mbx on 2010 does not have a calendar app in teams. So mailbox should be on ex16 as requirement.

@fatshark_2k As I mentioned in a previous post, according to this article,  the requirement are:

- sync running

- Oauth configured properly

- At least, Exchange 2016 cu3

But nothing states clearly that the mailboxes have to reside on Exchange 2016 in a multi exchange environnement.

And again, if I move a mailbox from 2010 db to 2016 db, the issue persist..... Whereas if I create a mailbox directly on 2016 db, we have the expected behaviour with Teams calendar.


On your side, did you try to move a mailbox from ex2010 to ex2016, and see if the calendar  is showing up in Teams ?


@Rigs33 , I tested with following. I have Exchange 2010 and Exchange 2016 in 1 organization. CAS namespace points to Exhange 2016 (autodiscover/webmail). Hybrid and Oauth configured on Exchange 2016. When a mailbox is on Exchange 2010 then the user has no calendar app/button in Teams. When i move the same mailbox to Exchange 2016 the user has the calendar app/button in Teams.

Also stated in your article in the matrix is states 'User's mailbox is hosted in' and then for on-prem the requirement is Exchange 2016 Cu3+ so the mailbox has to be hosted in Exchange 2016 cu3+ 




Did you ever find a solution here?  I have a very similar problem with an onpremise Exchange 2013 and 2019 with hybrid setup between Online and 2019 box.  Moving users from onprem 2013 to 2019 is not getting me the calendars button in Teams for those users

Best Response confirmed by ThereseSolimeno (Microsoft)

Hello @fishizza,


I had a long troubleshoot session with a Microsoft Exchange Escalation Engineer, it appears that the Teams Rest/API protocol  is not compatible with mailboxes created in Exchange prior to 2016 CU3.
Finally, we migrated mailboxes directly to Office 365.