MailStore – “EWS Error Code: The remote server returned an error: (401) Unauthorized” when archive from Microsoft 365 mailboxes
ID: 13515
Summary
In MailStore, if you’re archiving from Microsoft 365 mailboxes, the following error occurs: “EWS Error Code: The remote server returned an error: (401) Unauthorized”
This issue was reported in (but may not be limited to):
- MailStore Server
- MailStore SPE
Cause
There is something wrong with the API permissions in Azure AD.
Resolution
Third-Party Issue
This is a third-party issue and cannot be resolved by MailStore.
Check the required API permissions: https://help.mailstore.com/en/server/Synchronizing_User_Accounts_with_Microsoft_365_(Modern_Authentication)