This article describes the steps and order to follow to transfer your domain between two Office 365 tenants.

1. Before the switch, modify MX record TTL to smallest time allowed.
2. Cloudiway configures 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

3. When you’re ready to switch, modify your MX records to point to the Cloudiway IP.
4. Run a final delta pass.
5. At this step, new mails arrive to the target and old mails are all migrated to the target. You’re now safe to detach the domains.
6. Run the script to remove domain from objects (see script in Move domain)
7. Remove Domain from Tenant.
8. Add domain to target tenant.
9. Add TXT DNS record.
10. Verify domain ownership.
11. You can now reassign the domains to the users: Modify SMTP and UPN on Target AD and sync the changes.
12. Modify your MX records to point to target Office 365.
13. The migration is completed.