TLS encrypted email "between servers"

Hi there, We use Cpanel/WHM extensively. We have a client (customer.co.uk) who has emailed us the following requirements: /**/ We wish to forward emails from our hosted email account (helpdesk@customer.co.uk) to one that you host. One of the requirements of our security department is that we establish a secure (TLS) connection between our servers. One part is, that emails forwarded to you - which originally came to the helpdesk@customer.co.uk address, are sent TLS encrypted from our servers to yours. For this kind of setup we have an administrative requirement that you confirm to us that an contractual relationship exists between you and Messagelabs, and that Messagelabs has been instructed to treat confidential emails from us as well, and that mails from their servers to yours are transmitted securely as well (as we have no way of checking that). /**/ Cpanel have responded as follows: This should be able to be set by setting tls_verify_hosts in exim.conf along with ensuring that hosts_avoid_tls is not set. These kinds of configurations are possible on an Exim server but the set up isn't something we'd be able to set and confirm. Some testing with the vendor would need to be done by your server administrators after settings have been made. Please refer to Exim documentation at [url=http://www.exim.org/exim-html-3.20/doc/html/spec_38.html]Exim Specification - 38. Encrypted SMTP connections using TLS/SSL and also these changes would need to be made in WHM under "Service Configuration "Exim Configuration Manager "Advanced Editor" to prevent the changes from being overwritten. I don't however follow where "Messagelabs" comes in? Is it just a case of setting up a VPS with Cpanel's mods above implemented? Any help appreciated. Cheers Dude