6. Select the 'More Settings' button from the lower right of the window
7. Click on the 'Advanced' Tab
8. Ensure that the Incoming server (IMAP) is set to SSL/TLS and the port is updated to 993
9. Ensure that the Outgoing server (SMTP) is set to STARTTLS and the port is updated to 587
10. Testing the account should work as expected (simple way is to send an email to someone and verify it moves from the outbox to the sent items)
Other email clients will need to be configured per their own instructions. Please find the configuration guide for your specific mail client to configure and enable security using SSL/TLS.
Setup on iPhone: https://support.apple.com/en-us/HT201320
Setup on Android: https://clients.digitimber.com/knowledgebase/1/How-to-setup-email-on-an-Android.html
Note: If you are migrating from another provider, they may not have valid SSL certificates for your domain. This will result in a warning:
Simply click 'Yes' to continue using the server. This will be resolved once the DNS and email migration is complete.