My email client of choice. I approach all of my email tasks in GTD style. Keeping my email inbox close to 0 at all times.
Airmail provides quite a good set of onscreen keys that you can use to do various actions on mails.
I also automatically sort newsletters into mailboxes so they never show up in my Inbox and I have to visit my
News mailbox whenever I want to read these emails. This is a rule set of how you can set it up for yourself: