Mail Checker for Proton Mail is a versatile browser add-on designed for Chrome that enhances the user experience with Proton Mail. This tool allows users to check their inbox directly from the toolbar, showing unread counts, notifications, and message previews. It supports multiple accounts with customizable features such as labels and colors. Users can read, reply, forward, and compose emails, complete with a rich text editor and end-to-end encryption for secure communication. Additionally, it supports OpenPGP for attachment decryption and offers various viewing modes for emails.

The add-on includes useful features like calendar invite detection for easy RSVP, two-factor authentication for enhanced security, and customizable desktop notifications. Users can also enjoy a range of user interface themes and settings synchronization across devices. The tool prioritizes user privacy, ensuring no data collection and direct API calls to Proton Mail servers. Quick actions and customizable compose options further streamline email management, making this add-on a powerful tool for Proton Mail users.