Send & Receive Issues

How to Route Email from an Old Domain After a Company Name Change

Natalie Taylor Sep 30, 2026 870 views

Question details

Users need to receive messages sent to their previous email addresses after a Microsoft 365 domain migration resulting from a company name change.

How to Route Email from an Old Domain After a Company Name Change

Product: Microsoft 365
Device & OS: not provided
Scenario: A company has updated its name and migrated to a new domain, but wants to guarantee that external emails sent to the old domain addresses are still delivered seamlessly to employees.
Observed behavior: Messages directed to the old domain must be successfully routed to the user's primary mailbox without requiring additional licenses.

Before you start

Ensure you have global or Exchange administrator privileges in Microsoft 365, and verify that the old domain remains active and verified in your admin center.

Solution 1Recommended

Add the Old Email Address as an Alias in Microsoft 365

Set the employee's new email address as the primary one while retaining the old address as an alias to guarantee continuous email delivery without extra licensing costs.

By configuring an email alias, Microsoft 365 automatically catches any mail sent to the old domain and redirects it to the user's current inbox.

It is crucial to keep the old domain active in your Microsoft 365 tenant; if the domain is removed or expires, emails sent to it will bounce back, regardless of the alias settings.

Access the Microsoft 365 Admin Center

Log in to the Microsoft 365 admin center using your administrator credentials and navigate to the 'Users' > 'Active users' section.

Select the Target User

Find and select the employee whose email address you need to manage. A side panel with their account details will appear.

Manage Email Addresses

Click on 'Manage username and email' under the 'Account' tab to view their current primary email and aliases.

Set New Primary and Keep Old Alias

Change the primary email address to the new company domain. In the 'Aliases' section below, ensure the old email address is added and retained.

Save and Allow Propagation

Save your changes. Note that it may take some time (usually up to 24 hours) for the alias updates to fully propagate across the global email system.

Add the Old Email Address as an Alias in Microsoft 365

No Extra License Required: Using aliases allows your employees to receive emails across multiple addresses using a single Microsoft 365 mailbox license, saving the company money.

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Frequently Asked Questions

Do I need to pay for an extra license to keep the old email address active?

No. As long as the old email address is set up as an alias on the user's primary mailbox, it does not require an additional Microsoft 365 license.

Can employees reply to emails using their old domain address?

Yes, Microsoft 365 supports sending emails from an alias. Administrators must enable the 'Send from alias' feature in the Exchange Admin Center. Once enabled, users can select the old address from the 'From' dropdown menu when composing a message.

What happens if I remove the old domain from Microsoft 365 entirely?

If you remove or unverify the old domain in the admin center, any emails sent to addresses using that domain will bounce back to the sender as undeliverable, even if the alias was previously configured in the user's settings.

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