Manage Domains (MS-100)

Add and Configure Additional Domains

  1. Login to Https://
  2. Go to Setup -> Domains
  3. Click + Add Domain
  4. Enter the Domain name and click Next.

Now you must confirm the ownership of the domain by verifying it.

Verify Custom Domain

  • In the next Screen you’ll see DNS records you need to add to your DNS provider to verify the ownership

You can either use a TXT record or MX Record, add one of these to your DNS wait for replication and click Verify, then next.


Configure Workloads For New Domain Name

  • Now in the next screen, you’ll see the below options,
  1. You can choose Add the DNS records for me as all the records will added for you ( You have to authorize the office 365’s access to your DNS account on the pop up window that appears when you click next.
  2. If you choose, I’ll add the DNS records myself, then you’ll see the list of records you need to add.
  • After the above selection you must choose what services you’re going to use, depending on its office 365 or you will add the necessary records  shown to your DNS zone.
  • Once DNS record are added, click verify to complete the process.

List of DNS records Needed for above Services,

Domain Verification TXT or MX record
Exchange Online   CName record
MX record
SPF Record  
Skype for Business Online   SRV Record CName Record  
Mobile Device Management for Office 365   Cname Record  


Configure User Identities For New Domain Name

  • Now  you can start modifying the all user’s UPN to allow them to use the new custom domain as their login, if required.

     Or, you can add them as secondary address depending on your organization needs.

Your options will be different depending on the old/new portal views

  1. Go to Users – > Active Users in the Admin Portal
  2. Choose Manage username to set a UPN , then save changes
  • If you want to add an Alias of customer domain, choose manage email alias- > Add an Alias -> click Save Changes.


Set Primary Domain Name

You can choose a domain to be the default  suffix used by the user accounts,

  1. Go to SetUp -> Domains from the admin portal
  2. Click on the domain you want to set as your default domain
  3. Now click Set as Default

Design Domain Name Configuration

You can add multiple domains and use them for different services.

You can add addresses with different suffixes to users to get emails from those domains in a single mailbox.

You can subdomain for example, if you want your IT team email to be different you can sub domains like and set it as suffix for IT users.

Points to remember:

  1. You must be a Global Administrator of a business or enterprise plan to add, modify or remove domains.
  • Microsoft 365 can support up to 900 domains in a subscription.
  • About your initial  .onmicrosoft domain,
  1. You can’t rename the onmicrosoft domain name once the subscription is created with it.
  2. You can’t rename your team site URL as it’s based on your domain name.
  3. You can’t remove your onmicrosoft domain.
  • Text record or MX record is required to verify the ownership of the custom domain.
  • You should be a global admin to edit UPNs ( If not, You’ll get the error We’re sorry, the user couldn’t be edited. Review the user information and try again)