Email migration checklist in 15 steps

A mail migration rarely fails at the copying itself. Most often the problem is something forgotten before or after it. This list covers the whole process in 15 steps, from the inventory to switching off the old server.

Before the migration

1. List every mailbox: personal, shared, aliases, distribution lists and technical mailboxes (for example for a scanner, a printer or company systems).
2. Write down what else uses the mail: forwards, rules, autoresponders, signatures and systems (CRM, shop, monitoring) that send from your domain.
3. Check mailbox sizes and the largest messages, to estimate how much data has to be moved and how long it will take.
4. Make sure you have access to the domain's DNS and decide who changes the records on switch day. A day earlier lower the TTL of the MX records to 300 seconds.
5. Notify users: when, for how long and what they have to do afterwards (for example set up their phone again). Ask them not to change passwords meanwhile.

Copying and testing

6. Back up the critical mailboxes (a PST export or a server-side copy) in case something goes wrong.
7. Move 1–3 pilot mailboxes first and check folders, dates, attachments, special characters and the calendar. In Loomigrate the free test is for that.
8. Run the full copy of all mailboxes in the background, outside working hours, and watch the report. Mail still arrives at the old server.

The switch

9. Right before the change run a last delta sync, to move the new messages.
10. Change the MX record to the new provider and remove the old MX records.
11. Update SPF, add DKIM and set up DMARC, so messages from your domain do not end up in spam. Add the autodiscover record too.
12. Set up Outlook and users' phones for the new accounts and check sending and receiving.

After the migration

13. Compare the message counts in the folders on both sides (the verification report) and ask a few users to check important messages.
14. For a few days repeat the delta sync, to catch messages that reached the old server after the MX change because of DNS delay.
15. Only after a week or two, when nothing is missing, switch off the old server and keep a backup for an agreed period. Review permissions and remove the accounts of former employees.

The most common pitfalls

• A TTL that is too high: part of the mail still goes to the old server for a day.
• Forgotten shared mailboxes and aliases: mail to them suddenly bounces.
• No DKIM and DMARC: messages from the new mail land in recipients' spam.
• Migrating during intensive work: slower copying and more messages to catch up.
• No way back: until the switch the old server has to keep working, and the MX record can be reverted within minutes.

How Loomigrate helps

A report with live progress, verification of the item count on the destination side, resuming of interrupted migrations and 30 days of free resyncs after completion cover steps 7, 8, 9, 13 and 14. You can test the first 200 items from 3 mailboxes for free.

Frequently asked questions