Steve Losh has an extensive and easy to understand post on working through the install of mutt, offlineimap, notmuch, and just about everything you would want to know about the subject.
Now that Sparrow is effectively dead many of its users will be looking for a new email client. If you’re not afraid of the terminal you may want to give Mutt a try.
While he’s inspired me to combine all my email to a single address, and simply not care which account responds to the message, after using mutt cold turkey for a day, I simply can’t do it. On days like tonight, with the Presidential Debate in full swing, pressing “o” to refresh my mail every 2 minutes simply doesn’t work. For my needs, right now, Sparrow is just fine. Let’s hope it stays that way.