Microsoft 365 and IMAP backup
Osiris backs up Exchange Online mailboxes (mail, calendar and contacts) and OneDrive, incrementally through the Microsoft Graph API, and any IMAP mailbox over IMAP, password-authenticated today (OAuth2 sign-in for Microsoft 365- or Google-hosted IMAP sources is in development). Every restore drawn from that backup is logged: who ran it, when, for whom, and from where.
How the Microsoft 365 side works
Backup runs incrementally via Microsoft Graph's delta-query mechanism, so a normal run only fetches what changed since the last one instead of re-scanning a whole mailbox or OneDrive. Users, mailboxes and OneDrives come in automatically through Entra ID directory sync (Graph users/delta), with the protected scope controlled per tenant: everyone, a specific group, or an exclusion list. Microsoft throttles the Graph API, especially for a large tenant's first backup. Osiris shows that wait instead of hiding it, the same honesty rule that applies to every other progress or limit in the product.
How the IMAP side works
Any IMAP mailbox is a valid backup source, authenticated today with a password. OAuth2 sign-in for IMAP sources hosted on Microsoft 365 or Google is in development, not available yet. IMAP-only tenants (ones without an Entra ID directory to sync from) are added by a manual mailbox list or CSV import instead.
Stated limits, not hidden ones
- Microsoft Teams messages are not part of the current scope.
- An IMAP source currently uses one login for all mailboxes under it (a master account or shared credentials); separate per-mailbox credentials, and OAuth2 sign-in as an alternative to a password, are both in development.
- SharePoint, Google Workspace, Exchange Public Folders and PST import are deliberately out of scope for now: see theroadmap for what's planned after.
Frequently asked
How does Osiris back up Microsoft 365?
Incrementally, through the Microsoft Graph API: Exchange Online mail, calendar and contacts, and OneDrive, tracked with Graph's own delta-query mechanism so a run only fetches what changed since the last one, not a full re-scan every time.
Does Osiris back up Microsoft Teams?
No. Teams messages are explicitly out of scope for the current version, stated on the roadmap, not silently left out.
How does IMAP backup work?
Password authentication today, one password per IMAP source. OAuth2 sign-in for Microsoft 365- or Google-hosted IMAP sources is in development. IMAP tenants without directory sync (i.e. not Microsoft 365) are added by a manual list or CSV import.