SMTP settings onm Support Assist

We've recently run into an issue with our support assist alerting us. Our corporate email server has had some slight amendments which we've been assured shouldn't have made a difference,. When we use our normal settings over port 25 (which did work), we now get: Unable to connect to SMTP server because of an authentication issue with the SSL certificate. Please ensure that a valid SSL certificate is installed before trying again We notice at the bottom, there is some text saying the server uses a secure method of data transfer. Traffic passes through firewall. Someone has mentioned TLS1.2??? If we change and use Port 465, we get a different message and no traffic reaches the firewall: Unable to verify the connection status because of an internal error. If the problem persists, please contact Dell technical support for assistance Any help most appreciated, especially as I'm worried any notifications of issues will not work.