You try to remove or make a change to a distribution group by using the Exchange admin center in Microsoft Exchange Online for Microsoft Office 365 or in on-premises Microsoft Exchange Server. In this situation, you receive the following error message:
You don't have sufficient permissions. This operation can only be performed by a manager of the group.
This issue occurs if you're not a manager of the group. In this situation, you're not listed in the ManagedBy attribute.
To learn about managing distribution groups that are synced to Office 365 from the on-premises environment, see the following Microsoft Knowledge Base article:
2417592 Owners of an on-premises distribution group that's synced to Office 365 can't manage the distribution group in Exchange Online