We were unable to manage a Distribution List in Exchange. A user submitted a ticket that they had sent an email to the DL but it was denied. The fix in the past was to remove the old DL created in AD and then recreate it in Exchange with full management capabilities. So the DL was deleted in AD and them a full import was done in OKTA to receive the changes in AD and sync through to O365 but this didn't complete and the DL still exists the alternative is to create a new DL with a different Email address. Not ideal as the users will get confused and this will create other issues when they use the wrong DL that is still in the GAL.