An alias is an extra email address for the same mailbox. That way John also receives email at j.peters@contoso.com, info@contoso.com or john@newdomain.com after a name change or acquisition, without needing a second mailbox. This article shows how to add an alias in the Microsoft 365 admin center, the Exchange admin center, with PowerShell or in on-premises Active Directory, and what to do when the alias doesn't work.
When do you use an alias?
- A name change, for example after a marriage: the old address keeps working.
- A new or extra domain after an acquisition or rebranding.
- Spelling variants of a name, such as j.peters and john.peters.
Do several people need to read the same mail? Then an alias isn't the right choice. Use a shared mailbox or a distribution group instead.
In the Microsoft 365 admin center
- Go to admin.microsoft.com > Users > Active users and select the user.
- On the Account tab, select Manage username and email.
- Under aliases, type the new address, choose the domain and select Add > Save changes.
In the same place you can also set an alias as the primary address: the address the user sends from by default.
In the Exchange admin center
- Go to admin.exchange.microsoft.com > Recipients > Mailboxes.
- Select the mailbox and, in the details pane, select Manage email address types.
- Select Add email address type, choose SMTP, type the address and save.
This also works for shared mailboxes and resource mailboxes. For distribution groups you'll find the same under Recipients > Groups. Exact menu names can differ slightly.
With PowerShell
Connect with Connect-ExchangeOnline and add the alias:
Set-Mailbox -Identity john@contoso.com -EmailAddresses @{Add="smtp:j.peters@contoso.com"}
Note: uppercase SMTP: makes the address the primary address, lowercase smtp: makes it an alias. Other handy variants:
- Remove:
@{Remove="smtp:j.peters@contoso.com"} - Check:
Get-Mailbox john@contoso.com | Select-Object -ExpandProperty EmailAddresses - Microsoft 365 group:
Set-UnifiedGroup; distribution group:Set-DistributionGroup, with the same-EmailAddressesparameter.
PowerShell really pays off when you give dozens of users an alias on a new domain at once, for example with a CSV file and a foreach loop.
Users from on-premises Active Directory
Is the user synced with Entra Connect? Then you can't add the alias in Microsoft 365: the field is greyed out or your change gets overwritten. Add it in Active Directory to the proxyAddresses attribute:
- Open Active Directory Users and Computers and turn on View > Advanced Features.
- Open the user > Attribute Editor tab > proxyAddresses.
- Add
smtp:j.peters@contoso.com. The primary address is listed withSMTP:. - Wait for the next sync, or start an Entra Connect sync manually.
In a hybrid Exchange environment, use your on-premises Exchange admin center or Set-RemoteMailbox instead, so Exchange and AD stay consistent. See create a mailbox in a hybrid Exchange environment.
Alternative: plus addressing
Only need a throwaway address for a newsletter or web shop? Exchange Online supports plus addressing: mail to john+webshop@contoso.com simply lands in John's mailbox, without an admin adding anything. An Outlook rule can sort those messages automatically.
Alias not working?
- Domain not available: the alias domain must be verified in Microsoft 365. Read add a domain.
- Address already in use: an address can belong to only one object. Find it in the Exchange admin center and remove it there first.
- Mail doesn't arrive yet: a new alias can take a little while to work everywhere. Wait an hour and test again.
FAQ
Does an alias need an extra licence?
No. An alias is free. You can add up to 400 per mailbox.
Can I send from the alias too?
By default Outlook replies from the primary address. To send from the alias, read send from an alias.
Can I sign in with an alias?
No, you sign in with the username (UPN). An alias is only for receiving email.
Nederlandstalige versie: Een e-mailalias toevoegen in Microsoft 365, Exchange of Active Directory