My email is running through a VPS and as most people I know do not use encryption, I wanted a way to add additional security to the stored messages on the server without increasing complexity/end user burden too much. Here I've used openssl s/mime but gpg would work too. The downsides are the same as any encrypted messaging system - forgetting key pw and security of the key. While it may not be "NSA proof", its a step up from leaving imap/pop messages in the clear on a server I do not physically control. Hope its a useful starting point for those who might be looking for something similar.