01
No mail proxy
The client talks to your providers. S² Mail is not a required middlebox for reading or sending. You do not need an S² account to use the app.
Security & privacy
Privacy by default. Security by architecture.
S² Mail is a client for mail you already own. We do not need your messages in order for the product to work, and we do not sit in the middle of Gmail, Microsoft 365, IMAP, or JMAP.
02
Encrypted on your machine
Sensitive local data is encrypted by default. Credentials sit behind the OS key store. Raw MIME and attachments live in an encrypted blob store, not in a plaintext folder.
03
Untrusted HTML
Email HTML is treated as hostile: sanitized, sandboxed, no Node access, strict CSP. Remote images and tracking are blocked by default.
04
Telemetry you can turn off
Analytics, crash reports, and diagnostics are separate switches. Turn them all off and nothing is sent. Complete opt-out is mandatory, not a buried setting.
05
We do not hold your master key
Device pairing and recovery are designed so S² never stores the key that unlocks your local data. If recovery exists, it is zero-knowledge on our side.
06
Quiet, signed updates
Stable updates are automatic for most people. Update checks do not include mail, credentials, or search history.
What this means in practice
Use S² Mail without creating an S² account. Credentials stay in the operating system vault. Message HTML never gets Node or filesystem access. If you turn analytics, crash reports, and diagnostics off, the client sends nothing. Legal detail lives in the privacy policy.