How to Add an Email Alias in Microsoft 365

An email alias is an extra address that delivers to a mailbox you already have. Add sales@ as an alias on a user, and mail sent to sales@ drops into that person’s inbox alongside everything else — no second mailbox, no extra license. It’s the simplest way to catch mail at several addresses without building anything new.

This walkthrough covers adding an alias in the Microsoft 365 admin center and with PowerShell, the difference between an alias and the primary address, and the part people get wrong: whether you can actually send from the alias. Aliases are cheap and useful, but they behave differently from a shared mailbox, so it’s worth being clear about what they do.

Alias vs primary address#

A mailbox can carry many SMTP addresses. Exactly one of them is the primary address — the default From address on outgoing mail and the one Microsoft 365 treats as the identity of the mailbox. Every other address is a proxy address, which most people just call an alias.

Mail sent to any of those addresses lands in the same inbox. The difference is direction: incoming mail to an alias works automatically, but outgoing mail goes out from the primary address unless you take extra steps.

Option 1: Add an alias in the admin center#

This is the quickest path and fine for most situations.

1. Sign in to the Microsoft 365 admin center (admin.microsoft.com).
2. Go to Users → Active users and select the person.
3. On the account panel, open Manage email aliases (under the Account or Mail area, depending on tenant).
4. Under Aliases, type the new address, pick a verified domain, and click Add.
5. Click Save changes.

The new alias starts receiving mail within a few minutes. You can add several at once before saving.

Option 2: Add an alias with PowerShell#

PowerShell is the better route when you’re adding aliases in bulk or scripting onboarding. The alias lives in the mailbox’s EmailAddresses collection.

Connect-ExchangeOnline

# Add an alias without disturbing the existing addresses
Set-Mailbox -Identity [email protected] `
  -EmailAddresses @{add="[email protected]"}

# Confirm the result
Get-Mailbox -Identity [email protected] | Select-Object -ExpandProperty EmailAddresses

Using the @{add=...} syntax matters: it appends the alias and leaves the other addresses alone. If you assign the whole -EmailAddresses list directly, you replace every address on the mailbox, which is an easy way to wipe out the primary by accident.

To make an alias the new primary address, add the replacement with an uppercase prefix and demote the old one:

Set-Mailbox -Identity [email protected] `
  -EmailAddresses @{add="SMTP:[email protected]"; remove="SMTP:[email protected]"}

Sending from an alias#

Here’s the part that surprises people. By default, even though mail arrives at every alias, mail leaves from the primary address. For a long time Microsoft 365 had no supported way to reply from an alias at all.

Microsoft later added support for sending from an alias, but it isn’t on everywhere and depends on the client. To use it, the feature has to be enabled for the organization, and the Outlook client has to be a version that honors the chosen From address.

# Organization-wide setting that allows sending from aliases
Set-OrganizationConfig -SendFromAliasEnabled $true

Even with this enabled, behavior varies between new Outlook, classic Outlook, and Outlook on the web, so test it before you tell a customer-facing team to rely on it.

Alias vs shared mailbox vs distribution group#

These three get mixed up constantly because they all “make mail go to more than one place.” They don’t do the same job.

If one person should receive mail at several addresses, use an alias. If a team needs to work a common inbox together, use a shared mailbox. If you just want to fan a message out to everyone’s personal inbox, use a distribution group. They’re often combined — for example, an alias on a shared mailbox.

An alias is not the sign-in name#

A point that trips up a lot of admins: the primary SMTP address and the sign-in name (UPN) are two separate things, even when they happen to look identical. Adding or promoting an alias changes the addresses mail is delivered to and sent from. It does not change the username someone types to log in.

So if you add [email protected] as an alias and even promote it to primary, that person still signs in with whatever their UPN was — often the original [email protected]. If you want the sign-in name to match the new address too, that’s a separate change to the user’s username, not something the alias touches.

Removing or changing an alias#

Removing an alias is the same EmailAddresses collection in reverse. Use the remove syntax so you only drop the one address and leave the rest alone:

Set-Mailbox -Identity "[email protected]" `
  -EmailAddresses @{remove="[email protected]"}

You can’t remove the primary address directly — promote another address to primary first, then remove the old one. In the admin center, the same action lives under Manage email aliases, where each alias has a remove option next to it. Give removed addresses a little thought first: if mail is still arriving at an old alias, deleting it means those senders start bouncing, so it’s often safer to leave a retired alias in place than to reclaim it.

Verify the alias works#

Don’t mark the ticket done until you’ve confirmed mail actually flows.

If a test message to the alias doesn’t arrive at all, work through Microsoft 365 email not sending or receiving to rule out mail flow and DNS before blaming the alias itself. You can also use message trace in Exchange Online to see exactly where a test message went.

Wrapping up#

An alias is the lightweight option: one mailbox, several receiving addresses, no extra cost. Add it in the admin center for a one-off or with Set-Mailbox -EmailAddresses @{add=...} when you’re doing several. Just keep the two big caveats in mind — incoming mail to an alias always works, but sending from an alias needs the org setting enabled and a client that supports it, and an alias is not a substitute for a shared mailbox when a team needs to work one inbox together.