While backing up a Mailbox, the job will complete successfully but your Cirrus Backup logs say completed with a warning: Failed to find group owner account.
When you review your completed Cirrus Backup, which include Microsoft Exchange items, you may end up with the warning message shown in the Session Logs.
Processing mailbox <name> completed with warning: Failed to find group owner account
Cirrus is unable to impersonate Office 365 groups (mail-enabled and security groups) that do not have an owner assigned. This is a known Veeam and Microsoft issue, as described in this Veeam article.
Please assign an owner to each of the Office 365 groups you wish to have backed up. The steps to achieve this can be found in this Microsoft article.
Help & Support
If you have followed the steps outlined above and the issue recurs in the next backup cycle, or you need help performing these changes, you can access online help at https://support.cirrusbackup.com or reach out to our Support team via firstname.lastname@example.org.
If you are unsure of how to check your backup session logs, please see the following: View Backup Logs.