RESOLVER.ADR.ExRecipNotFound; not found

I've tried deleting and re-creating the DG. I've also cleared the outlook autocomplete cache as some posts have suggested. This hasn't resolved the problem.

It appears that external emails are coming through okay but internally we receive a bounce back. Also, rules that reference the domain no longer work correctly.

We are using Office365 Small Business and Outlook 2013.

Does anyone have any additional suggestions?

Thanks

Carl