Checker Plus for Gmail (Chrome, Firefox, and Edge) allows you to see notifications, read, listen to, or delete emails.
Checker Plus works without opening Gmail and supports the management of multiple accounts. This extension/add-on is a great way to continue browsing without the need to bring up Gmail to manage your emails.
Checker Plus Features:
See the people emailing you just like in the Gmail chat notification, with an option to show their contact photos or your assigned photos for them
Voice notification: If you get an email while you're busy watching a movie or cooking dinner, this extension can optionally read it out loud, i.e., "Jason says, dinner at my place" It's great for the visually impaired
Option to monitor any Gmail or custom labels
Option to run in this notifier in the background when Google Chrome is closed and still get new email alerts
Popup mail preview window to read, archive, mark as read, or delete emails without leaving the current tab (or option to go directly to your Gmail tab)
Supports offline view
Desktop sound or voice notifications when new mail arrives or add your own sounds
Support for multiple Gmail and Google Apps accounts