Moving your company email to Microsoft 365 sounds risky — but with the right order of operations, no message is lost and there's no gap in service. The trick isn't the copy; it's the sequence. Here's the plan we use for a clean cutover.
Before you start: lower your DNS TTL
A few days ahead, lower the TTL (time to live) on your MX record to something small like 300 seconds. That way, when you flip email over at the end, the change propagates in minutes instead of hours. While you're at it, inventory everything: every mailbox, alias, shared mailbox, distribution list, and roughly how much mail each one holds.
Step 1 — Set up Microsoft 365 and verify your domain
Buy the right licenses, then add your domain in the Microsoft 365 admin center and verify it with the TXT record Microsoft provides. Verifying your domain does not affect live mail flow — your existing email keeps working normally throughout setup.
Step 2 — Create mailboxes and migrate existing mail
Create each user, shared mailbox, and group. Then copy your existing mail across using the method that matches your old system — an IMAP migration works for most providers; cutover or staged migration for on-premises Exchange. This runs in the background while your current email keeps flowing, so there's no interruption yet.
Step 3 — Cut over MX (the actual switch)
Once mail is copied, change your MX record to point at Microsoft 365 and add the autodiscover CNAME. From this moment, new mail flows into 365. Because you lowered the TTL earlier, this takes minutes. Do a final delta sync afterward to catch any messages that arrived mid-cutover.
Step 4 — Lock in deliverability
This is the step people skip — and it's the number-one reason migrated email suddenly lands in spam. Update your SPF record to authorize Microsoft, turn on DKIM signing, and add a DMARC policy. We walk through all three in this guide.
Step 5 — Reconnect devices
Reconfigure Outlook, phones, and anything that sends mail through your domain — apps, CRMs, even copiers and scanners. Then confirm you can send and receive from every account.
The riskiest part isn't the migration — it's the order. Cut MX over too early and mail splits between two systems; skip SPF/DKIM/DMARC and it lands in spam. If a no-downtime move matters, we do these every week.