Problem adding one or more people to the group when you add an external contact as a guest in Microsoft 365

• Applies to:

  Exchange Online

Original KB number:   4054864

Symptoms

When you try to add a guest user to a Microsoft 365 group, you receive the following error message:

There was a problem adding one or more people to the group. For help, contact your administrator.

Cause

This issue occurs if the guest user who is being added already exists in Microsoft Entra ID.

Workaround 1

Delete the user object from the on-premises directory.

Note

This is the preferred method.

Workaround 2

Replace the user with a mail contact. To do this, save the user properties, delete the user object, and then create a mail contact that has the same properties.

Note

When the guest is invited, a new user object is created in Microsoft Entra ID, and the object coexists together with the mail contact.

Workaround 3

Move the user object to an organizational unit (OU) in the on-premises directory, and then exclude that OU from synchronizing through Microsoft Entra Connector.

Note

This behavior deletes the user object from Microsoft Entra ID, but keeps it available in the on-premises directory. After you make these changes, the guest user can be added to group.