Number of unread emails on system tray

Make the system tray icon was showing the number of unread emails.  
 ![](https://d2r1vs3d9006ap.cloudfront.net/s3_images/1668734/RackMultipart20171103-115812-1p7ua87-tray_inline.jpg?1509698084 "Image: https://d2r1vs3d9006ap.cloudfront.net/s3\_images/1668734/RackMultipart20171103-115812-1p7ua87-tray\_inline.jpg?1509698084")