Office 365 backups for Exchange Online might report errors backing up group mailboxes

When viewing Exchange Online backups in the Command Center, you might observe the job Completing with Errors on group mailboxes.

Symptoms

When viewing Failed Items on you might see group mailboxes reporting one of the following issues:

• Too many concurrent connections opened
• Mailbox does not exist

Note: Backups of the group mailboxes might initially report an error, and then complete after a few subsequent jobs/retries.

Causes

Commvault opened a case with Microsoft to review:

• Backup job fails for group mailboxes if group mailboxes and their members are backed up in the same job. If you run backups of group mailboxes separately, the jobs complete.
• Microsoft Exchange APIs fail to open NON-IPM folders (contacts, calendar) of a group mailbox with an error.

Resolution

Commvault has worked with Microsoft and jointly came up with a solution.

To resolve the issue, please apply the latest Maintenance Release package for your Commvault Version.