We use Zimbra at work. I'd have a hard time recommending it unless you really, really want 80% of Exchange and 40% of the usability.
(Outlook Web Access is still the only webmail client I've found that is in GMail's ballpark. Since running an Exchange server is beyond my skillset, my interest, and my budget, and trusting a managed Exchange host feels odd--at that point I might as well just stick with GMail. So I do.
Google isn't going to find anything particularly interesting about me by my mail, anyway.)
"[Gmail/Facebook/USGov/etc] isn't going to find anything particularly interesting about me by my mail, anyway."
There are two problems here:
1. We look at our data from our point of view. Other people and orgs have their own points of view, and it's their actions driven by their points of view that we need to worry and think about. For example, you think your mail is uninteresting, yet Google enhances the value of their ads by correlating your interests with the interests in your communication network.
Government surveillance can also learn a lot just by recording and analyzing who you talk to. When a law enforcement agency cannot get a full wiretap warrant, they will sometimes settle for a pen register, which just records the telephone numbers of your calls. This allows them to find out who you know, and who you talk to the most. This lets them form more detailed opinions about you and your known associates, which may or may not be accurate. You know, like Google does for ads.
Oh, you're just not that interesting to the government?
2. Innocent behavior being observed by the government is enough to disrupt your life in minor and major ways. Consider the British couple that was recently denied entry to the United States, merely because their tweets contained boisterous comments about destroying the US (i.e. partying really hard), and digging up Marilyn Monroe's grave. Imagine if they had used the British slang term "crack."
It takes nothing more than mere notice to disrupt your life. If you innocently have communication with someone who in turn has communication with a "person of interest," you could find your car carrying a GPS. Just from noting communication networks, never mind the communication content.
I'm not trying to go all tinfoil hat, I'm just suggesting that your view of your data is completely different from corporate and government's view of your data. You could be served an ad (horror!), or you could be served a warrant (horror), based on accurate or mistaken interpretation of any facet of your communication.
Yeah, but it's also email. You could delete every email you've ever created and everyone who's ever saved their copy still has their copy.
Even if you were trying to be all sneaky about your email by having your own service set up somewhere, you're still making copies of everything you send by virtue of sending it. It's more vectors for the government/Evil Google/whoever to need to scan to get a picture of the data you're creating, but it's not impossible.
I know you're just making a point, but to the people who actually are all tinfoil hat, this whole conversation to shift to whether or not you should even use email as a method of communicating.
A mischaracterization (and, given your tone, probably intentionally so).
A useful mail system has value to me. It outweighs the (in my mind vastly overhyped) dangers of Google doing something nefarious with my data. If you disagree, you're welcome to run your own mail server. Nobody's stopping you.
