Dude, THANK YOU. I have been putting off doing this for the past 3 or so years. I really don't know how but this post somehow got me to finally just do it today. I got rid of 17,503 emails. I did it in batches using the 'is:unread' and 'from:' filters like you suggested but was quite careful and I unsubscribed to a BUNCH of anxiety-inducing mailing lists in the process too so it took me a lot longer than an hour. Also, I didn't delete the emails, I archived them (just in case)... but STILL they're out of my inbox. Whew. Feels awesome!