Inbox Zero is a practice that helps you get inputs out of the way in order to communicate well and concentrate on the things that really matter. You don’t just get rid of the unread count, you get rid of the mental clutter as well.
See an email. Respond + archive, forward + archive, star/flag/send to task manager + archive or just archive. Or delete.
The first steps will be the most difficult (especially if your inbox count is in the thousands), but it gets easier as you go. Routine is important.
Use folders or labels if you need to, otherwise just use the search function. Gmail’s search is best.
Further reading: