How to sync email

Hello cdotb,

You can resolve iCloud Mail issues on your devices by completing the steps listed here: If iCloud Mail isn't working - Apple Support that are also listed below.

"Things to check first

1. Check the system status of iCloud Mail.
2. Check that you turned on iCloud Mail:

• On your Mac, open the Mail app then choose Mail >Preferences. Click Accounts, then select your iCloud account in the sidebar. Under Account Information, make sure that the account is turned on and the status is online. 
• On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud and check that Mail is turned on. 

1. Make sure you that haven't exceeded your iCloud storage limit. If you exceed your iCloud storage limit, learn how to make more space available in iCloud. 
2. Make sure that you're using the latest version of software on your device. "

Best regards

Happened to me too. I had to delete my Mail account (settings, mail) and re-add it. Once I did than, syncing worked again.