IMAP Mail Notifier is a Firefox browser extension that monitors IMAP email accounts and shows desktop notifications when new mail arrives.
Data collected and transmitted

To check for unread mail, the extension sends the following data to a proxy server operated by the author (mymail.rumin.info):
IMAP server hostname
Email address
Password

This data is transmitted exclusively over HTTPS (encrypted). It is used solely to establish a connection to your IMAP server and retrieve the unread message count and the date of the latest unread message.
Data storage

The proxy server does not store, log, or share your credentials or any information about your mailbox. No email content is read. The data is used only to perform the IMAP check and is discarded immediately after the response is returned to the extension.

Your account credentials are stored locally in your browser using the standard browser.storage.local API and never leave your device except for the IMAP check request described above.
Third parties

No data is shared with any third party. The proxy server connects only to the IMAP server you specify in the extension settings.