New iPhone email lag

New iPhone XR on latest iOS version. Cox email account correctly set up with both incoming and outgoing servers, ports, SSL, ID and PW.

I can see new emails arrive via the Cox web client but they don’t download to the native iOS mail client sometimes for many hours.

This is not a password issue. Account has been added and deleted many times on the phone. Once re-created it will get all current inbox items but then starts lagging again.