The "Connect to EWS: SOAP header Action was not understood" error occurs when validating an Office 365 Organization

Challenge

When adding or editing an Office 365 organization, the following unexpected error occurs: "Connect to EWS: SOAP header Action was not understood".

Cause

The error may occur when establishing a connection to the Exchange Web Services (EWS).

Solution

As a workaround, you can temporarily assign a mailbox to your service account that is used to add or back up an Office 365 organization.

If you cannot assign a mailbox to your service account due to license limitations, contact Veeam Technical Support.