I think you either define "most" differently than I do or you may benefit from speaking to nontechnical people about their computer usage. Keywords that may be appropriate: the Google Hotmail.
Firefox Sync encrypts the data locally, and you can run your own server. There's actually a simplified one for running on your own home server (as opposed to the large Mozilla infrastructure).
I've been baulking at Firefox 4's "sync" today because the data is on their server with their key. A bit 1990's me thinks.
There's no way I'm trusting my email, or anyone else's, to another third party.
I imagine I manage this like most folk, I forward gmail to my server and procmail from there. Works great.