Exchange Hybrid and Teams-Calendar not useable

Question

Hello,

we are using an Exchange Hybrid with two Exchange 2016 CU21 in a DAG with KEMP in front of them. The HCW and AADConnect are running without errors. Mailbox onboarding and mail flow is successful.

In Teams the calendar button is visable, but the calendars show empty for on premise users.

We followed all troubleshooting steps listed on the following site: teams-exchange-interaction-issue
All steps are successful including the "Teams" and "FreeBusy" checks out of testconnectivity.microsoft.com.
We also verified the external access via EWSEditor and used a cloud-migrated mailbox to verify free/busy out of EXO-OWA to an on premise mailbox calendar.

Teams Calendar is not able to display mailboxes of OnPremise users. We tried with Teams App and via WebApp.
Has anyone any idea?

Kind regards
Steve

Answer 1

We solved it.

At the firewall was a forgotten setting with country blocking active. After adding an exception for the Microsoft Teams IP-ranges it works now.

Thx.

Answer 2

@Anonymous

I would suggest you check whether Exchange online mailbox could access Exchange mailbox calendar from OWA/Outlook first.

If you cannot see Exchange on-premises calendar from Outlook/OWA, it means there may exist issue with Exchange hybrid, we could follow this article to narrow down it: Cloud user can't see On-premises user's Free/Busy

If Exchange online mailbox could see Exchange on-premises mailbox calendar. It means this issue related with the teams setting, we could follow this article to narrow down it: Configuring Teams calendar access for Exchange on-premises mailboxes

---

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.