After moving mailboxes from Exchange 2007 to 2010 users have been unable to make modifications to distribution groups. Users are listed on both "Managed by" and "Security" tabs in AD and the "Group Information" tab in Exchange 2010. We tried to recreate the DL on Exchange 2010 but it did not resolve the issue. The Exchange 2007 server is still operational and after moving the users mailbox back to Exchange 2007 they were able to modify the distribution lists. Any idea what could be causing mailboxes on Exchange 2010 to not have modify rights on distribution lists?