Move a Domain Between Office 365 Tenants
Migrate domains without email downtime using Cloudiway's mail routing.
Three-Phase Domain Migration
Overview
The Challenge
A domain can be attached to only one Office 365 tenant at a time. This creates a challenge: how do you transfer a domain without losing emails during the transition?
The Solution
Cloudiway's mail routing platform forwards emails during the domain transition, ensuring no mail is lost while the domain is being moved from one tenant to another.
DNS Preparation
Phase 1: Mailbox Migration
First, migrate all user mailboxes from the source tenant to the target tenant. Use Cloudiway's migration platform for this step.
Recommended: Big Bang Migration
For fastest results, migrate all mailboxes in a single operation. This approach minimizes the time spent in the transition phase and reduces complexity.
Phase 2: Mail Routing Setup
Configure Cloudiway's mail routing platform to forward emails from the source domain to the target tenant's onmicrosoft.com addresses.
How Mail Routing Works
user@company.com → Cloudiway → user@tenant2.onmicrosoft.com This ensures all emails sent to user@company.com are delivered to the user's new mailbox in the target tenant while the domain is being transferred.
Phase 3: Domain Transfer
Rename Users in Source Tenant
Execute a PowerShell script to reassign all user accounts from company.com addresses to temporary onmicrosoft.com addresses.
# Change primary SMTP from @company.com to @source.onmicrosoft.com
Wait for Replication
Allow propagation time after removing the domain from the source tenant. This typically takes 15-60 minutes.
DNS Verification in Target Tenant
Add the TXT verification record in the target Office 365 admin portal to prove domain ownership.
Reassign Primary Addresses
Restore users' primary SMTP addresses to their company.com domain in the target tenant.
Update MX Records
Point MX records back to the target Office 365 tenant to complete the migration.
Done! Mail now flows directly to the target tenant.