How to Create a Mailbox Alias Assigned to Another Microsoft 365 Account
Question details
The user wants a mailbox to receive messages sent to an email address that is currently assigned to a separate, non-mailbox account.
- Product
- Microsoft 365 Exchange
- Device & OS
- not provided
- Scenario
- Managing email routing and aliases across two separate Microsoft 365 accounts where one account lacks a mailbox.
- Observed behavior
- An email address cannot be assigned as an alias to two different accounts simultaneously, preventing direct shared delivery without configuration changes.
Ensure you have administrator privileges in the Microsoft 365 admin center to modify Exchange recipient settings and manage mail forwarding rules.
Configure Email Forwarding in Exchange Admin Center
Use this method if both Microsoft 365 accounts must remain active and retain their current email addresses.
Since Microsoft 365 does not allow the same email alias to exist on two separate accounts simultaneously, forwarding emails from the non-mailbox account to the mailbox account is the most effective workaround.
Log in to the Microsoft 365 admin center using your administrator credentials and navigate to the Exchange admin center.
In the left-hand navigation menu, click on 'Recipients' and select 'Mailboxes'.
Locate and click on the non-mailbox account that currently holds the target email address.
Click on 'Manage email forwarding' in the properties pane, check the box to forward emails, and specify the email address of the destination mailbox.
Remove and Reassign the Email Alias
Use this approach if the target email address can be safely removed from the original non-mailbox account.
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Frequently Asked Questions
Can I use the same email alias on two different Microsoft 365 accounts?
No, Microsoft 365 architecture dictates that an email address must be entirely unique across your tenant. It cannot be assigned as an alias to two separate accounts simultaneously.
Will emails forward if the original account does not have a mailbox license?
Depending on your specific Microsoft 365 setup, you may need to convert the original address into a Shared Mailbox or ensure it has minimal routing privileges before Exchange can successfully process forwarding rules.
How long does it take for a new alias or forwarding rule to take effect?
Changes made in the Microsoft 365 Exchange admin center usually take effect within a few minutes, but Microsoft advises that backend synchronization can occasionally take up to 24 hours to propagate fully.
