In the screen capture below we have the "Incoming server settings".

Under the Security settings, the dropdown contains options for "SSL/TLS" and "STARTTLS", either of which may be used.

Under Authentication another dropdown appears, and that contains options for "NORMAL" and "ENCRYPTED".

• If your mail client offers "ENCRYPTED", what that will do is to enforce a dual-level of encryption.
  
  
• If you end up using "NORMAL", that's ok because your e-mail password is still encrypted based on the other settings.

The checkbox labeled "Require sign-in" appears to be the author's implementation of "SMTP Authentication Required". Be sure to select this option, as it is MANDATORY.

Under Authentication another dropdown appears, and that contains options for "NORMAL", ''ENCRYPTED" and "CLIENT CERTIFICATE".

• If the options in your mail client are similar to these, try ''ENCRYPTED". If that won't work, try "NORMAL".
  
  
• If you end up using "NORMAL", that's ok because your e-mail password is still encrypted based on the other settings.
  
  
• The "CLIENT CERTIFICATE" option is probably not a realistic choice in our network, nor is it really needed