Backup of Microsoft 365 group mailbox fails with:
Cannot back up the primary mailbox of an Microsoft 365 user: '[ews-code=ErrorNonPrimarySmtpAddress]: The primary SMTP address must be specified when referencing a mailbox.'
Cannot back up the primary mailbox of an Microsoft 365 user: '[ews-code=ErrorNonExistentMailbox]: The SMTP address has no mailbox associated with it.'
Cannot get the user's email address for connecting to the Microsoft 365 group mailbox. At least one group owner is required to back up or recover the group mailbox. An owner must be a licensed user. If the group's visibility is 'private' or 'hiddenmembership', the owner must also be a member of the group.
Group messages are skipped from the team backup.
Check the following:
- Group owner needs to have licensed mailbox
- Group owner must be member of the group
To resolve the issue:
Alternatively, you can replace the group owner with a user that fulfills the requirements given above:
- Go to https://login.microsoftonline.com and log in to your Microsoft 365 account.
- From the home page go to Microsoft 365 admin center.
- In the left menu, select Groups:
- In the list of groups, select the one which backup failed due to the problem described above.
- In group details, go to Members tab:
- Click View all and manage owners:
- Add a licensed user who has a mailbox to the list of group owners. For private groups - to the list of group members.