Penguin Mail reads Gmail, Outlook.com and Microsoft 365 accounts, and any IMAP or POP3 account with SMTP, such as Fastmail, iCloud and Yahoo, and finds the server settings for you. It syncs from the system tray, shows your accounts in one inbox or one at a time, and keeps your mail on your own computer.

• One inbox for every account, with Gmail's categories, Outlook's Focused and Other tabs, labels and search
• A calendar with Google Calendar, Outlook and any CalDAV server: Day, Week, Month and Agenda views, invitations answered in the mail, and reminders
• Contacts from Google, Outlook and any CardDAV server
• A composer that shows formatting as you write, with Undo Send and Send Later
• Flags in seven colors, VIPs, smart mailboxes and reminders
• Rules and automatic replies for every account, kept on Gmail, Outlook or a Sieve server, or run by the app on its own
• Plus addresses to give out instead of your own
• OpenPGP and S/MIME signing and encryption through your own GnuPG
• Remote images blocked until you ask for them
• An assistant that runs on a local model or on Claude, off until you pick one
• Every control named for screen readers and reachable from the keyboard

Adding a Gmail or Microsoft account takes one sign-in in your browser. Penguin Mail is built with GTK and libadwaita and fits best on GNOME, but it runs on any Linux desktop.