Knowledge Base

Office 365 group mailboxes are not being backed up

Problem:

CodeTwo Backup fails to create a backup copy of an Office 365 group mailbox. You receive the following error:

Couldn’t connect to Office 365 group mailbox '{email}' because the group is private and there are no mailbox-enabled users added as owners or members to that group.

Solution:

Office 365 users can be assigned as owners or members to Office 365 groups. If the group is private, only owners and members can access its contents, and only group owners can add new members. Normally, an Office 365 group has at least one owner. However, in may happen that the user who is the only owner of an Office 365 group is deleted from Office 365 or no longer has access to a mailbox. In such a case, and provided that the group is private and there are no other members assigned to it, it will not be possible to back up the mailbox of that Office 365 group because the program cannot access its contents.

The quickest way to back up the problematic Office 365 group mailbox is to assign at least one owner or member to that group. However, keep in mind that the user who will be assigned the owner or member role needs to have a mailbox, i.e. you need to assign an Exchange Online license to that user. Once you assign an owner or member to the group, you will be able to back up the group's mailbox practically instantly.

Another solution is to change the Office 365 group from private to public. However, remember that once the group is public, all your Office 365 users can join that group and access its contents. As opposed to the first solution, you need to wait at least an hour (or sometimes longer) for the changes to propagate across Office 365 before you attempt to back up that Office 365 group mailbox. 

Follow the links below to perform at least one of the following:

Assigning an owner or a member to an Office 365 group

  1. Log in to Microsoft 365 admin center (Office 365 admin center).
  2. Expand the Groups section on the left-hand navigation menu and click Groups.
  3. On the Groups page, click the name of an Office 365 group whose mailbox you want to back up (e.g. Backup, as shown in Fig. 1.). The details pane will appear on the right side of the screen.

Selecting a group in Microsoft 365 admin center
Fig. 1. The details pane of an Office 365 group.

  1. On the group's details pane, go to the Members tab and click View all and manage owners to add owners (Fig. 2.) or View all and manage members to add members to the group. You need to add at least one owner or member.

Members tab on the details pane of an Office 365 group.
Fig. 2. Accessing the list of all Office 365 group owners.

  1. On the page that opens, click +Add owners (or +Add members), select at least one user from the list (or use the search box to look for a particular user) and click Save (Fig. 3.). It doesn't matter which user you select, as long as that user has a working mailbox (i.e. is assigned an Exchange Online license).

Adding owners to an Office 365 group
Fig. 3. Adding owners to an Office 365 group.

  1. Once done, you can close the group's details pane.

You should now be able to back up the mailbox connected to that Office 365 group.

Changing an Office 365 group from private to public

  1. Log in to Microsoft 365 admin center (Office 365 admin center).
  2. Expand the Groups section on the left-hand navigation menu and click Groups.
  3. On the Groups page, click the name of an Office 365 group whose mailbox you want to back up (e.g. Backup, as shown in Fig. 1.). The details pane will appear on the right side of the screen.
  4. On the group's details pane, go to the Settings tab, select Public under Privacy, and click Save.

Changing the privacy settings of an Office 365 group
Fig. 4. Changing the privacy settings of an Office 365 group.

  1. Once done, you can close the group's details pane.

Before you attempt to back up the mailbox connected to that Office 365 group, you should wait at least an hour for the privacy settings to propagate across Office 365.