Changing the From Domain in Office 365

Last reviewed on February 13, 2015   —  10 comments

Microsoft Office 365 Change From domainAn Office 365 user was trying to make Outlook use his vanity domain as the From address instead of the Office 365 default domain (

This is not something that is controlled from Outlook, its set on the server. While you can have multiple addresses assigned to your mailbox (and receive mail sent to those addresses) Outlook always uses the default SMTP address assigned to the Exchange account as the address for replies or new messages.

In a local Exchange server, changing it is as easy as the administrator logging into the server and changing a mailbox policy. It usually takes longer to log in than it does to make the change.

In Office 365, the administrator can log in and change individual users or use a cmdlet to change the domain used by all users. If the account you want to change is the administrator account (common among SOHO users), you either need to make a new admin account and log in with it to reassign the primary email address of the first account or use the set-mailbox cmdlet.

If you choose to create a second administrator account, you do not need to assign a mailbox to it (therefore, no license is needed). It won’t be used for receiving email and will not be using Office 365 outside of the administration panel. If you are purchasing more than one account, you can (and probably should) make at least one of the other accounts an administrator. Do not delete the account, especially if you have already set up the other online services.

These steps assume you’ve already added the domain to the online account and your account has administrator permissions.

  1. Login into
  2. Click users & groups
  3. Double click on the user name whose address you want to change
  4. Click details
    Change the domain name for a user
  5. Select a different domain from the domain name list for the User name.
  6. Click Save

Using the set-mailbox cmdlet takes a little longer but will be faster if there are a large number of addresses to change, since you can use a CSV to update the addresses.

  1. You’ll need to configure PowerShell to connect over the Internet. If you don’t use Windows 7 or Windows 2008 R2, you may need to uninstall PowerShell and install the current version. See Install and Configure Windows PowerShell – if using Windows7 or 2008 R2, skip to Step 4 in these instructions.
  2. Establish a connection to the online server. See Connect Windows PowerShell to the Service for details.
  3. Run the Set-Mailbox cmdlets for the users that need changed from addresses to your domain addresses. The cmdlet is formatted like this:
    Set-Mailbox diane -EmailAddresses

For more information and instructions to change multiple users using the cmdlet, see
Change a User’s Primary E-mail Address

The easy way to avoid this hassle is to create the Office 365 account, add your vanity domain (and set it as the default domain) then add users and mailboxes, however, many people want to try Office365 before they move their existing domain to the service and use the initial administrator account for email during the trial.

Fortunately, you can change the default domain for new accounts in the portal or with a cmdlet (cmdlet is only available in the on-premise Exchange 2013).

Set the Default Domain for New Accounts

You can set the default domain for new users in the Office 365 Admin Center.

Login to the portal, click Domains. Select the domain that you want to set as default then click the Set as default link on the right.

This screenshot is from an E account; Business accounts are similar but may be missing the left bar.
Change the default domain

If you prefer to use a cmdlet, you’ll use the Set-AcceptedDomain cmdlet (available in on-premise only).

Set-AcceptedDomain -Identity -MakeDefault $true

About Diane Poremsky

Diane Poremsky
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

Please post long or more complicated questions at Outlook forums by

10 responses to “Changing the From Domain in Office 365”

  1. martin

    I tried to follow this, Office 365 user but i am getting an error message
    The proxy address "SMTP:xxxxx@yyyyy" is already being used by xxxxxx_561b7d978b". Please choose another proxy address.
    any help would be really appreciated


    1. Diane Poremsky

      You should only get this error is the alias is already in user with another account. You can have multiple uses of the same alias as long as they are in different domains. For example, I have two domains hosted in my Office 365 hosting account and have diane@ set up in both. The one has numbers tacked on the end, like in your example.

  2. Scott

    Hi Diane, I see there are many related posts but I cant find the exact one for my situation. I have an office 365 account and have set up two domains and My user's primary email address is however there are times I want to SEND FROM from outlook desktop application. How can I do this? Thanks, Scott

    1. Diane Poremsky

      You'd need to create a pop3 account to use the non-default address. Most people either use DL's or shared mailboxes for the secondary addresses instead. Short version: remove second address from mailbox, create a dl, assign that address. Make your user the only member of the DL and give it send as permission. When you want to send from the address, select the DL in the from field. I'll write up instructions this afternoon.

    2. Diane Poremsky

      I forgot, you can also use a utility. I have some listed here: Exchange Server and Secondary Email Addresses

  3. scott

    Thank you Diane, the DL method is fine for what I need. Cheers!

  4. Niels

    Hello Diane,

    I have 2 users and one shared mailbox in my office365: (siteadmin)

    I want user A and B both, to automatically open the shared mailbox account. Ifwant them both to send as the info account.

    Is this possible and can you tell me how? I get lost looking for a solution online.

    1. Diane Poremsky

      You need to give them both full access to the shared mailbox and sendas permissions.
      Instructions to use powershell are here - - or you can do it using the office 365 portal.

  5. Tim

    Hi, Diane, we've been on O365 since the middle of last year and even though we added our vanity domain and have manually set our users' primary SMTP: addresses to use the vanity domain, our new users still come up with and we have to manually change those as well. Is there a default setting we can change so that all new user accounts set primary SMTP: to the vanity domain?


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