Most migration horror stories start the same way: the migration ran, but nobody checked these five things first. After resolving 1,000+ migration issues across enterprise environments, I know where the gaps are.

Identity readiness before any batch runs. Verify UPN alignment, Entra ID attributes, and Azure AD Connect sync status. Mismatched identities cause more migration failures than anything else on this list.

Mailbox permission audit before migration. Document every delegate access relationship, shared mailbox membership, and resource mailbox configuration. BitTitan doesn’t carry these over automatically in every scenario. If you haven’t mapped them, you’ll find out at cutover.

DNS and mail flow before domain migration. MX records, SPF, DKIM, and Autodiscover all need to be confirmed in the target environment. Silent mail routing failures start here and are among the hardest to diagnose after the fact.

Licenses pre-assigned before mailbox migration runs. Licensing gaps produce access failures that look like tool errors. They aren’t. Pre-assign and confirm before the batch touches a single mailbox.

User communication confirmed before cutover. Verify that users have received and acknowledged the cutover instructions, Outlook reconfiguration steps, and mobile enrollment requirements. Assumed communication is not communication.

PowerShell can automate parts of all five checks. It still takes an experienced engineer to read the output and know what it’s actually telling you.

Pre-migration checks aren’t overhead. They’re the difference between ten support tickets and a hundred.

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