Why doesn't XPhone Federation work with Microsoft Teams?

Problem:

XPhone Federation with Microsoft Teams does not work, although all settings in XPhone and in the customer's firewall are correct.

If the customer's Teams domains are not hosted directly by Microsoft, but by an external domain provider which is connected to Microsoft's Teams tenant, this this may be the cause of the above-mentioned problem.

This behavior affects all customers who connect their externally hosted domain to a Microsoft tenant.

Solution:

To make Microsoft Teams accessible via the customer domains, the following DNS entry must be configured in each customer domain:

This entry causes XPhone Federation to be able to find the Teams Federation Server using the customer domain name.

Then check whether federation between XPhone and the customer domains now works as desired.