An open-source email client for iPhone that looks and feels like a texting app, while keeping real email underneath. Standards-only, no backend, free. iPad is next.
Zirbe is German for the Swiss stone pine, the pine of the Alps. The name continues a lineage of text-mode mail clients that runs Elm → Pine → Alpine, and lands on another pine. The hidden meaning is the point: it reads like a coined word and rewards anyone who looks it up.
A conversation in Zirbe is an email thread, not a person. A thread is
identified by the RFC 5322 Message-ID, In-Reply-To, and References
headers and shown like a named group chat: the subject is the title, the
people on From/To/Cc are the members, and each message is one bubble in
time order. The same person writing five different-subject threads produces
five conversations, which is correct email behavior. Starting a new
conversation requires naming it, and that name is the subject.
Apple Messages is the aesthetic muse, never a clone. We implement only what the email RFCs define (5321 SMTP, 5322 message format, 2045/2046/2047 MIME) and nothing that isn't email: no video or voice calls, no shared notes, tasks, or team workspaces. The CheckIn privacy posture carries over wholesale: no backend, no third-party SDKs, no telemetry. Credentials and tokens live in the Keychain, device-bound, never synced off the device that obtained them. The only network destinations are the user's own mail servers and identity providers.
Zirbe 1.0 is on the App Store, iPhone-only for now, and connects to any IMAP/SMTP account with a password or app-specific password. It reads and sends mail, threads it into conversations, handles attachments and inline images, and covers the surrounding surface a daily mail app needs: folders, archive and move, drafts, junk and block-sender, search, pinning, reactions, voice messages, and local new-mail notifications. The full picture of what is built and what is next is in BACKLOG.md.
The mail engine is Cocoanetics/SwiftMail,
a mature actor-based async IMAP and SMTP client, consumed through a thin adapter
in Packages/ZirbeMail (a MailEngine actor returning Zirbe-owned value types,
so the engine stays swappable). Email content parsing — HTML to text, quote
folding, signatures, inline images — comes from the shared
Klartext package.
Next up is an iPad split-view layout, then multiple accounts and an integrated inbox, then OAuth for the providers that are retiring app passwords.
MIT. See LICENSE.