Chatmail
A private, self-hosted email client
Chatmail is a personal email client that shows the operator's own mailboxes as simple conversations, with a priority inbox, tags, rules and quick replies.
It is not a public service. It runs on the operator's own computer, is reachable only over the operator's private network, and sign-in is limited to an allow-list of the operator's own accounts. There is no sign-up.
Chatmail connects to Google accounts with Google Sign-In so it can read, organise and send email from the operator's own Gmail and Google Workspace mailboxes, and add events to the operator's Google Calendar.