does what it says on the tin. it notifies you when you have unread emails. HOWEVER, recently there was an update that locked MANY previously free features behind a $20 USD paywall (despite the fact that the popup CLAIMS you can donate ANY amount, i guess $19 and lower doesn't count as any).
These features aren't anything advanced either, any and all customization, changing what buttons appear on the popup, the works. Way shittier add-on. Use only as a notification bell that opens gmail and nothing else.