Q: No incoming Mail on Mac after installing El Capitain on my iPhone

After installing El Capitan on my iPhone 5s (due to messages keep not sending/ being received) I now cannot receive any mail on my phone or Mac although the settings have not changed. Any ideas please?

I have called my internet provider who confirm my settings are correct. I've also tried connection Doctor and all Green.

I'm not keen to update my Mac to El Capitan as I don't trust it won't cause more problems.