Graphite Mail

Graphite Mail is a free, open-source mail, calendar and contacts client for Microsoft 365,
personal Microsoft accounts (outlook.com, hotmail.com, live.com), Gmail and any IMAP
provider (Yahoo, iCloud, Zoho, Fastmail, AOL or a custom server).

Your mailbox is stored on this computer, in a folder you choose: read, search, reply,
file and plan while offline, and your changes are sent when you reconnect, in order,
with retries. Several accounts at once with an All Inboxes view, a calendar with
invitations and Teams / Meet meetings, your organisation's directory, Outlook rules and
Gmail filters, Bcc, signatures, attachments, drafts, six themes and keyboard shortcuts.

No server of its own, no telemetry: the app talks to your provider directly. Sign-in
tokens and app passwords live only in your system keyring (GNOME Keyring or KWallet).
Because the snap is strictly confined, give it access to the keyring once:

 sudo snap connect graphite-mail:password-manager-service

Email HTML is shown in a script-less sandbox, remote images are blocked until you allow
them, and links open in your web browser.