Changing the From Domain in Office 365

Last reviewed on April 24, 2014

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 (onmicrosoft.com).

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 onmicrosoft.com 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 portal.microsoftonline.com
  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 @onmicrosoft.com addresses to your domain addresses. The cmdlet is formatted like this:
    Set-Mailbox diane -EmailAddresses SMTP:diane@my-domain.com

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 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.

Written by

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 Outlookforums.

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

  1. martin

    Diane
    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

    martin

  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 @a.com and @b.com. My user's primary email address is scott@a.com however there are times I want to SEND FROM scott@b.com from outlook desktop application. How can I do this? Thanks, Scott

  3. scott

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

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