[Exchange] Why do I get the error "Insecure mail server (starting with http) not supported"?

You are getting this error because the mail server address you provided connects over insecure HTTP whereas in efforts to protect your identity and your emails, our app does not support this insecure protocol.

Please provide a mail-server address, which connects over secure protocol (HTTPS) or get in touch with your Mail-Server Administration team if you do not have that information.