Email migration checklist: moving to the cloud without losing mail.

Email is the one system everybody notices instantly. A careful migration is nearly invisible to users.

Before you start

• List all mailboxes, shared mailboxes, aliases, distribution lists and resources.
• Record current mail flow: MX records, SPF, DKIM, DMARC, relays and devices that send mail, such as scanners and applications.
• Check mailbox sizes, archive locations and PST files.
• Decide on retention, security and sign-in methods, including multi-factor authentication.

Prepare the target

Create the tenant, verify domains, set security baselines, create users and groups, and test with a pilot group.

Migrate in stages

Move mail in batches, starting with pilot users. Sync mailboxes ahead of the switch so only a small delta remains at cut-over.

Cut over

Lower DNS TTLs in advance. On the day, change MX records, update SPF and DKIM, and watch mail flow. Reconfigure phones, Outlook profiles and any systems that relay mail.

After the switch

Run a final sync, confirm nothing is stuck in queues, update documentation and retire the old system only after a safe interval.

Common pitfalls

Forgotten shared mailboxes, scanners that stop sending, auto-complete cache confusion in Outlook, and users who have not been told what to expect.

Communication

Tell users when, what will change, what they must do and who to contact. Calm users make smooth migrations.