The error "Members can't remove themselves from security groups. Please set the group to Closed for requests to leave." when editing a distribution group.

Issue: Customer is the owner of a distribution group called Testgroup
When trying to add employees from Outlook he gets the following error message:
Changes to the public group memberships cannot be saved; You do not have permission to perform the operation on the object


Cause: This happens, because the distribution group the user wants to modify was created on Exchange server 2007. Type this command from PowerShell to confirm that distribution group has legacy version attribute:
get-distributionGroup testgroup | Fl *Version


This is legacy version:  ExchangeVersion : 0.1 (8.0.535.0)

Solution: The distribution group needs to be updated to later exchange version. Use  Exchange server 2010 or 2013 PowerShell  to update the Exchange version attribute of the distribution group
From Exchange 2013 or Exchange 2010 powershell, type Set-distributiongroup TestGroup. That command updates the exchange version for the DG.


To Verify, type:  get-distributionGroup testgroup | Fl *Version


Version should now display ExchangeVersion: 0.10 (14.0.100.0)