Don't litter in inbox
Most of the people don't even know what is an inbox. Their inboxes are filled with over 5k emails and finding something useful is like finding a needle in haystack. So what is an inbox? Inbox is not the final place for you email, "inbox is a staging area where emails which needs some action to be taken" That's it.
Make labels and folders to keep the necessary email. For email that you might need in future just archive them and for all other un ncessary emails just click delete.
Some people even have thousands of subscriptions to weekly letter which they don't even open. Unsubscribe any letter which you haven't open even after one week.
This way you will always be on top which email needs you attention and you will feel bit relaxed.