I can't configure a PEC mail

Hi you all,
I am trying to install a PEC mail (certificated mail) on my eM client.
No problem at all with gmail mails.

Here I attach you the requirements, indications of my PEC mail:

And here my settings.

This is the error message.

What am I doing wrong?

The fix 

Thank you in advance!

please try changing the Server Security policy in both POP and SMTP tabs to “Use SSL/TLS on special port (legacy)” and let me know if the problem persists.

Best regards,