Update: 8/11 12:41 PM PT – This issue has been fully resolved. Messages sent while we were experiencing the issue are now being pushed through (and no messages should have been lost). Thank you for your patience!
We are currently experiencing Groups mail processing delays. We are working to isolate the cause of this issue and will post updates as we make progress.
As always, we sincerely apologize for any inconvenience this may cause your Groups.
Groups Community Manager