When connecting to my email address via outlook I get "The server you are connected to is using a security certificate that does not match its Internet Address. Do you want to continue using this server?". I understand this can be caused by man-in-the-middle attacks. I have been checking my email comfortably for years before this problem occurred. I am using:

pop3.live.com
port: 995
This server requires a secure &connection (SSL)
No Secure Password Authentication

smtp.live.com
Port: 25
This server requires a secure &connection (SSL)
Outgoing server requires authentication -> Use same settings as my incoming mail server

Have you changed certificates within the last month? Could you provide new details?