Postline is a program that runs on your computer. It is not a service, and there is no server operated by Postline that your mail passes through. That single fact answers most of what a privacy policy usually has to explain.
Last updated August 21, 2026
Nothing. Postline has no analytics, no crash reporting, no update check, and no phone-home of any kind. The only network hosts it contacts are Google’s OAuth endpoint, to sign you in, and Google’s Gmail API, to fetch and send your mail.
When you sign in, Postline requests two permissions: gmail.modify, which covers reading your mail and changing labels including archive, star, and moving to Trash, and gmail.send, which covers sending the messages you compose. It does not request the broader permission that would allow permanently deleting mail.
Message content is fetched to your machine, rendered in your terminal, and cached in a local SQLite database so the client can start instantly and stay usable offline. That cache lives in your user configuration directory and is never transmitted anywhere. Postline does not use your Google account data to train models, does not sell or share it, and has no ability to do either — the data never reaches anyone but you and Google.
OAuth tokens are stored in your operating system’s credential store: Keychain on macOS, Secret Service on Linux, Credential Manager on Windows. On a machine with no keychain available, they are written to an encrypted file using AES-256-GCM with a key derived from a passphrase you supply. The authorization itself uses PKCE and a loopback redirect on a random local port, so the exchange never leaves your machine.
HTML mail is converted to text locally and remote images are never fetched. Senders who embed tracking pixels learn nothing about whether you opened their message, because nothing is requested from their servers.
Running postline --logout erases the stored tokens and cached mail from your machine. You can also revoke Postline’s access at any time from your Google account permissions page, which takes effect immediately and independently of anything on your computer.
Postline’s use and transfer of information received from Google APIs will adhere to the Google API Services User Data Policy, including the Limited Use requirements. Gmail data is used only to provide the user-facing mail client: displaying messages, searching, changing labels, and sending mail you compose. It is not used to serve advertisements, is not sold, and is not transferred to any other application or person.
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