M365 AtlasSecure Microsoft 365 Mailbox Backups

Open-source CLI and SDK for encrypted, deduplicated mailbox backups to S3-compatible storage.

Per-Tenant Encryption

Each tenant gets a unique AES-256-GCM key derived via scrypt. Data stays encrypted even if storage is breached.

Messages and attachments are stored by SHA-256 hash per mailbox. Identical files are stored once.

S3/MinIO Object Lock with time-based retention enforced by storage itself, not app metadata.

Microsoft Graph delta queries for incremental backups with automatic full-scan fallback on interrupted runs.

Save backed-up emails as standard .eml files in compressed zip archives with Outlook-compatible folder structure.

Programmatic API for embedding in other Node.js applications via the m365-atlas/sdk subpath.