Are non-SSL SMTP connections allowed?

Question

Are non-SSL SMTP connections allowed?

Answer

By default, cPanel servers do not accept non-SSL connections from email clients. The "Require clients to connect with SSL or issue the STARTTLS command before they are allowed to authenticate with the server" setting in "Exim Configuration Manager" can be disabled to permit non-SSL connections from email clients. 

Additional resources

Exim Configuration Manager Basic Editor: Security