Microsoft 365 Email Migration

Microsoft 365, Office 365, Outlook.com, Hotmail, and hosted Exchange moves need special handling because modern auth, tenant policy, and mailbox throttling affect what the migration can do. Migration Monkey treats Microsoft mail as an OAuth mailbox bridge by default.

Auth Path

Exchange Online has moved away from basic username/password authentication for modern tenants, so Microsoft routes should expect OAuth or tenant-approved migration access. If the source is an older hosted Exchange or IMAP server, the tool can still quote an IMAP source into Microsoft 365 when that source supports IMAP.

What Gets Sized

• Mailbox GB, message count, and folder count.
• Number of users in the tenant or batch.
• Archive mailbox requirements and retention-policy effects.
• Tenant throttling, admin permission, and delta sync needs.
• MX, Autodiscover, SPF, DKIM, and DMARC cutover checks.

No-Custody Default

The preferred route copies between Microsoft and the destination provider directly. Migration Monkey records the operational evidence: OAuth route, consent, status, counts, warnings, retries, and billing ledger. Message bodies are not stored by Migration Monkey in normal mode.

Verification

Check inbox, sent, deleted, archive, custom folders, delegated/shared mailbox expectations, search results, and recent inbound mail after MX cutover. Microsoft tenant jobs often need a final delta pass after DNS and Autodiscover are stable.

Credit Notes

Microsoft 365 has a higher base than generic IMAP because OAuth, tenant policy, throttling, and admin validation increase operational work. Single-mailbox consumer moves can still fit inside the 500-credit range, while tenant batches, archive-heavy mailboxes, and assisted relay price higher.