I use GMail with the understanding that Google has access to my activity and content. However, I trust Google to not divulge* my activity and content to other email recipients and senders. That's enough privacy for me in my normal email usage.

* disabling the option of blocking image-loading in the iOS GMail app is definitely an aggravating and inexplicable tactic, to the point I'm starting to looking into switching away from GMail as my provider.