Security model

Alcarta treats a connected mailbox as an external capability, not as data owned by an agent. Every request is bound to one organization, and mailbox grants are intersected with the caller’s token scopes before an operation runs.

Mailbox credentials are encrypted with a per-row data-encryption key using AES-256-GCM. A versioned key-encryption key wraps each data key, and authenticated data binds the ciphertext to its organization and row. Long-lived keys are loaded from files rather than environment variables. JWTs are signed with Ed25519 and include a key identifier for rotation.

Outbound provider, OAuth, and webhook URLs pass an egress guard. It blocks unsafe destinations both when a URL is saved and when it is used, reducing DNS rebinding and server-side request forgery risk. Keep network-level egress policy as an additional boundary.

Security-sensitive changes and mail actions are written to the append-only audit log. Each entry continues a hash chain, making removal or reordering detectable. Export and retain audit data under your own compliance policy.

For browser access, use the built-in organization roles and mailbox grants rather than sharing an administrator account. For agents, issue separate tokens with the narrowest practical scope and revoke them individually when a workload is retired.