While StartSSL is free, it isn’t a clear process to those that haven’t created a certificate before. Let us tell you how to walk through the site.
Anyone operating a server on any scale should want a digital certificate to encrypt data between clients and services, whether for personal, office, or public use. That’s a broad statement, but it holds true no matter how you slice it.
With so many people accessing networks over WiFi or other untrusted networks for an increasing number of different kinds of services—calendars, contacts, Webmail, email, and so on—encryption is a must, whether via a VPN or by securing services one by one. While I recommend VPNs, they aren’t always the practical, affordable, or correct solution. For remote email access, SSL/TLS is simpler and more straightforward, and you don’t have to compromise on protection in the process.
Source: Ars Technica