Message: "There is no default e-mail client available" when updating Microsoft Office 365 (April 24, 2020)

Observation

Since the Microsoft Office 365 update mentioned above, the ProCall Client for Windows MAPI can no longer initialize.

The following message window when starting the ProCall Client may be an indication of this:

Example screenshot: Note Microsoft Office Outlook

The message window may also appear if there are causes other than the problem described here.

Understanding the problem

With the test tool MFCMapi the problem can be traced. 

MFCMapi is a test tool to check the MAPI interface and to localize possible MAPI errors.

The tool can be found at https://github.com/stephenegriffin/mfcmapi.

Possible reason

Update to Microsoft Office version dated 24 April 2020 triggers this behavior.

Workaround

We have developed the following workarounds for the observed behavior:

• Change connection to Microsoft Outlook for the ProCall Client for Windows
  Disable MAPI and connect via EWS
• Adjust environment variables of the affected client system
  https://stackoverflow.com/questions/61469343/mapiinitialize-fails-after-april-24-2020-update-of-office-365
• Resetting to an earlier Microsoft Office version (before April 24, 2020)
  https://support.microsoft.com/en-us/help/2770432/how-to-revert-to-an-earlier-version-of-office-2013-or-office-2016-clic

Solution

None known. A solution cannot be found via ProCall Enterprise.

A fix must be provided by Microsoft.

Further information

• https://stackoverflow.com/questions/61469343/mapiinitialize-fails-after-april-24-2020-update-of-office-365