Are you overwhelmed by your inbox? Does it show that you have 10,000 messages in there, and 4,000 of them show as unread? If you find that this is a difficult situation to deal with and need a way to help organize things, consider the following method:
Over the past couple years, I've shifted toward a practice called "Inbox Zero." It's a strategy that helps you keep track of important emails and makes sure you remember the things you still need to address. The idea is that the only emails you have in your inbox are the outstanding items, and you don't want them in there. Maybe some of them are awaiting a response. Others might remind you of tasks you need to complete. Others might contain information you need to accomplish other tasks. The idea with this system is that once the email is no longer needed you get rid of it, with the goal of eventually getting down to zero emails in your inbox.
When I say "get rid of it," I don't necessarily mean to delete the email (although that's perfectly fine f you don't think you'll ever need that email again). I'm a bigger fan of filing that email away just in case I ever need it again.
GMail makes the practice of Inbox Zero a lot easier. When I'm done with an email, my preferred course of action is to "archive" it. In GMail, archiving is an option that merely removes the email from the inbox. The message is still retrievable, usually by search but also by looking at "All Mail," but it's not cluttering up my inbox, making it harder to focus on the tasks I have yet to complete.
If you're interested in trying this out, but don't know how to handle your thousands of emails, usually the best method is to simply move every single email out of your inbox. You can move them into another folder, delete them, whatever. You just need to get them out of your inbox. You might try moving everything older than a couple weeks, and then take the rest of your emails one at a time. Feel free to call me for help with this, particularly if you have a complicated email setup that syncs to all your devices.
After two or three years of practicing Inbox Zero, I certainly don't get down to zero all the time. I don't even get to it on a regular basis. On average, I'd say I have about 20 emails that need my attention, and this number will go up and down depending on how busy I am. But I'm happy to know that the only things in front of me are the ones I have to focus on.