Can I use more than one domain or address in Microsoft 365?

The short version

• Add each extra domain in the admin center and verify it, the same way as the first.
• Give people aliases on any verified domain. Microsoft charges nothing for them.
• Mail to an alias arrives in the person’s normal inbox.
• Outlook on the web can reply from the alias once an admin turns on a setting.
• When a domain’s MX record points to Microsoft 365, all mail for that domain goes there.

When does this come up?

Three common cases:

• A second brand or an old business name. You want mail to oldname.com and newname.com to reach the same people.
• A shorter or friendlier address. Jenna also wants jen@ to work.
• A role address only one person reads, like billing@ for the bookkeeper. If several people read it, use a shared mailbox instead.

How do I add another domain?

Microsoft’s domains FAQ says you can typically add up to 5,000 domains to one subscription, and subdomains too if you manage your own DNS.

1. In the Microsoft 365 admin center, go to Settings, then Domains.
2. Add the domain and add the TXT record Microsoft shows to prove you own it.
3. If the domain should receive mail in Microsoft 365, add its MX, Autodiscover and SPF records too. Our guide to moving-day DNS records lists them.

Microsoft warns that once you point a domain’s MX record at Microsoft 365, all mail sent to that domain goes there. If someone still uses a mailbox on that domain elsewhere, move them first.

To make a domain the default for new accounts, select it on the Domains page and choose Set as default. Microsoft notes this only affects new accounts.

How do I add an alias?

These steps follow Microsoft’s alias guide. You need an Exchange admin role.

1. In the admin center, go to Users, then Active users.
2. Select the person.
3. Under Aliases, select Manage username and email. (You won’t see this if they have no license.)
4. Type the new name in Username, pick a domain from the list, and select Add.
5. Select Save changes.

Expected result: within up to 24 hours, mail to the alias arrives in the person’s inbox. Microsoft allows up to 400 aliases per user, with no extra fees or licenses.

If the domain you want isn’t in the list, it hasn’t been added and verified yet.

Which address do replies come from?

This is the part that surprises people. Microsoft says the reply address depends on the app:

• Outlook on the web uses the alias the email was sent to.
• Outlook desktop uses the person’s primary address.

To let people choose an alias in the From box, an admin turns on Microsoft’s “send from aliases” setting for the organization. Microsoft documents it as the PowerShell command Set-OrganizationConfig -SendFromAliasEnabled $true. After that, each person picks which aliases to show in their Outlook settings. If your team mainly uses desktop Outlook, test replies before you print a new address on business cards.

Why does it matter?

Aliases cost nothing and save licenses. A second domain lets a rebranded business keep the old address working for years, so customers who still have old business cards can reach you. Doing it inside one Microsoft 365 account also means one set of logins, one admin and one bill.

What are the common mistakes?

• Using a full mailbox where an alias would do. That’s a license you don’t need.
• The same name on two domains for shared mailboxes. Microsoft’s shared mailbox page says info@domain1 and info@domain2 as two shared mailboxes cause an “already being used” error. Name the second one differently first, then rename it.
• Pointing MX for a domain someone else still uses. Their mail will start arriving in Microsoft 365.
• Bought through a partner? Microsoft says if your subscription came from GoDaddy or another partner, you may have to change the primary address in that partner’s console instead.

What if it didn’t work?

• “A parameter cannot be found…” error. Microsoft says setup for a new domain can take up to 4 hours to finish. Wait, then try again.
• The alias bounces. Wait up to 24 hours, then test from an outside address.
• Replies still come from the main address. That’s expected in desktop Outlook. Use Outlook on the web, or ask your admin about send-from-alias.

How much does it cost, and how long does it take?

Aliases and extra domains are included. You pay only for the domain registration itself, with whichever registrar you use. Adding an alias takes a minute; a new domain takes as long as its DNS records take to update.

How does E-3 handle this?

Pointing another domain or an old address at a website comes up about 90 times in our records, and extra domains for email follow the same care. For domains E-3 manages, the domain is registered to you, and we save the existing DNS records before adding anything for Microsoft 365.

Related questions

• Which DNS records change on moving day?
• Shared mailbox, distribution list or group?
• How do I get a new email address for a new employee?
• Can you point another domain at my website?
• Back to the complete Microsoft 365 guide

Sources

1. Add another email alias for a user (Microsoft Learn)
2. Domains FAQ (Microsoft Learn)
3. Add or remove email addresses for a mailbox in Exchange Online (Microsoft Learn)
4. About shared mailboxes (Microsoft Learn)