Struggling to get to inbox zero? The truth is that those newsletters you have been saving for weeks are old and obsolete anyway. Those emails waiting on your reply from more than a month ago? Well, if you haven't replied yet, they really did not need your reply.
This is a frightening thought for most people, and if you are the type of person who has not even purged your deleted email in years, this is going to be especially tough. But, just delete them. If this idea absolutely causes you anxiety, then consider creating an "Archive" or "Old Email" folder, then moving everything here for safekeeping. Revisit the folder next new year and see if you really needed them. You probably won't.