One of our clients is requiring that all emails sent to them be TLS Encrypted. I spoke with our email hosting company and they said that all emails are sent TLS if the end server allows it. Our client sent us a test email and had me return to them all of the header information. Apparently our test failed. Their response was this:
"While I do see TLS occuring between CLIENT_NAME_HERE and Postini, I do not see it between your mailserver and Postini. In order to ensure a message is secured during its path over the public internet, we need messages transmitted between your company and Postini to also be sent using TLS."
I am assuming that the postini server is our email hosting company. How can I make sure that our messages are being sent from each client machine to the pop3 server using TLS? I really don't know where to start. Does this involve purchasing a certificate from Verisign?