This article describes the steps and the order to follow to transfer your domain between two Office 365 tenants and to minimize downtime on inbound mail when using the Cloudiway Mail Routing tool.
Note that this tool requires Cloudiway Services assistance. You must reach out to Cloudiway Services at least 5 business day’s in advance to ensure availability to help you set up and test the mail router prior to your scheduled cutover.
- Before the switch, modify your MX record TTL to the smallest time allowed.
- Work with Cloudiway Services to configure mail routing between the source domain names and the technical target domain (eg: target.onmicrosoft.com sample):
Source SMTP Target SMTP company.com target.onmicrosoft.com company2.com target.onmicrosoft.com
- When you’re ready to switch, modify your MX records to point to the Cloudiway IP.
- Run a final delta pass.
- At this step, new emails will arrive to the target and old emails are all migrated to the target. You’re now safe to detach the domains.
- Run the script to remove the domain from objects (see script in Move domain)
- Remove Domain from Tenant.
- Add domain to the target tenant.
- Add TXT DNS record.
- Verify domain ownership.
- You can now reassign the domains to the users: Modify SMTP and UPN on Target AD and sync the changes.
- Modify your MX records to point to target Office 365.
- The migration is completed.