Under certain conditions, HIPA regulations require forced TLS for email communications. Banks, HR services, and Medical organizations normally have this requirement. Opportunistic TLS is not sufficient in these cases. Lack of forced TLS can be a complete roadblock for electronic communications with vendors, partners, and customers. (for a good explanation of the difference, see: http://www.rexconsulting.net/opportunistic-vs-required-tls.html)
SmartCloud needs the ability to provide forced TLS to designated domains. This might be best handled by requiring a PMR so as to protect SmartCloud administrators from accidentally or temporarily making a change that should not have been made. It also provides a more formal record of all such changes.
You can also review and vote on this at the post on Greenhouse.