Execution guide

Migrate to Fastmail without turning email into a live-fire experiment.

The safe sequence is inventory, prepare, import, authenticate, test, cut over and retain rollback. Changing MX records is near the end—not the beginning.

Before any change

Inventory the system that already exists.

Every human mailbox and owner Aliases, role addresses, catch-alls and forwarding rules Shared calendars, contacts and delegated access Automated senders, forms, invoicing and CRM services Current MX, SPF, DKIM and DMARC records Mobile devices and desktop mail clients Recovery accounts, DNS access and registrar ownership

Controlled sequence

Create the account structure

Create users, domains and required addresses before routing live mail. Do not assume an alias list can be reconstructed from memory.

Lower DNS TTL

Reduce relevant record TTL in advance where appropriate. Record the original values so they can be restored.

Import historical data

Use the documented migration tools for mail, calendars and contacts. Compare folder counts, recent messages and critical calendar events.

Configure authentication

Prepare SPF and DKIM and define a staged DMARC policy. Never publish multiple SPF records.

Test before MX

Test outbound mail, replies, calendar invitations, aliases, mobile access and sending from business applications.

Change MX records

Cut over only after every receiving address exists. Monitor both the old and new systems while DNS propagates.

Observe and reconcile

Check delivery, spam placement, authentication results, missing mail and user access. Keep a written incident log.

Retire slowly

Keep the previous provider accessible until imports, legal retention, forwarding and recovery have been verified.

Rollback trigger

Reverse the cutover when mail loss is plausible.

Rollback is justified when required addresses are missing, inbound delivery is inconsistent, authentication fails broadly or a business-critical sender cannot operate.

Rollback package

Original MX and authentication records
Named DNS owner with account access
Old provider kept active
Timestamped test messages
User and alias inventory
Decision owner authorised to reverse the change

Completion rule

A migration is complete when the business can prove mail flow, ownership and exit—not when the new inbox opens.

Open the domain checklist Recheck product fit

Primary evidence

Provider documentation checked for this decision.

Evidence reviewed 20 July 2026. Product details and commercial terms can change; verify final configuration with the provider.