Mail Access

Apple Mail for macOS

Instructions are suitable for macOS Sierra, High Sierra, Mojave and Catalina.
A video is available for more convenient understanding of procedure.

In order to setup correctly all the parameters you have to manually setup some fields in Preferences panel.
Follow as show below:

In Apple Mail open Preferences (Cmd+,)
or Mail/Preferences from Apple Mail contestual menu.
 

Deselect Automatically manage connection settings:
Change Incoming Mail Server (IMAP) port to 993 and leave all other preferences as is show below. 
Authentication: Password

Deselect Automatically manage connection settings:
Change Outgoing Mail Server (IMAP) port to 587 and leave all other preferences as is show below.
Authentication: Password

Click Save botton.
The procedure is completed.

Close all preferences windows and click "Save all changes"