IMAP Mail Notifier од Alex Rumin

IMAP Mail Notifier checks your IMAP mailboxes in the background and shows a desktop notification when new mail arrives. A badge on the extension icon displays the number of unread messages.

Features:
• Multiple accounts support
• Works with any IMAP server (Gmail, Yahoo, Yandex, Mail.ru, corporate mail, etc.)
• Desktop notifications with sender name and unread count
• Badge counter on the extension icon
• Enable/disable individual accounts without deleting them
• Import and export account settings as JSON

How it works:
Since browser extensions cannot open raw TCP connections, the extension uses a lightweight PHP proxy script to perform the IMAP check over HTTPS. The proxy is hosted by the author and communicates only with your IMAP server. No email content is accessed — only unread message count and the date of the latest unread message.

The source code of the proxy script (IMAP-notifier-checkmail.php) is included in the extension package and can be self-hosted on any PHP server with the IMAP extension enabled.