No, additional software is not required.

email2 is offered as SaaS, on-demand hosted solution. While we or your local technology reseller host your Private Email Network, we don’t replace any of the basic e-mail infrastructure you currently have in place. Once sent or retrieved, email2 messages are stored behind your firewall as any other e-mail message. Your company retains total and singular control over all of its own data.

//Edited June 2009