If you’re like me, sometimes you like to do things a little more efficiently and elegantly through PowerShell or through the Azure portal when it deals with the underlying infrastructure that’s associated with an Office 365 tenant. If you’re using Office 365 you’ve established a tenant with a .onmicrosoft.com name. Reminder PSA: You can’t change your tenant name after you’ve created it – at least not right now. But you can mask it using custom DNS names.
If you’re a little leery of Azure, then perhaps this will help to peel back the onion and bring tears of happiness to your face.
Step 0 – realize what you’re doing 🙂 and also that you probably want to make certain that you have permission to use the domain name that you’re setting up on the Office 365 / Azure instance that you’re going to perform these configuration changes on. Note that if you’re using a domain name already for something else that it might be wise to create a subdomain to tinker with rather than making “adjustments” to the main domain that you’ve got (e.g. something.danusher.com rather than danusher.com).
Step 1 – Head on over to your Office 365 admin portal (https://portal.office.com/adminportal/) and go to the bottom left corner to expand the “Admin Centers” section and click on “Azure Active Directory” (https://aad.portal.azure.com/binarybrewery.onmicrosoft.com). This will launch you to your Azure Active Directory admin center within Azure (alternatively, you can go to portal.azure.com and click on Azure Active Directory from the left most blade to open these settings).
Step 2 – Expand “Azure Active Directory” from the left most blade and then select “Custom domain names” from the blade that appears. This will list out the default tenant name that you have with your Office 365 tenant that was built out with your tenant when it was provisioned.

Step 3 – Add a custom domain by typing in the name of the domain and then determining if you want to use a TXT record or an MX record to verify that you own the domain. If you’re not familiar with how to edit your TXT or MX records, Microsoft has some handy documentation on this over on the Office 365 support documents – https://support.office.com/en-us/article/gather-the-information-you-need-to-create-office-365-dns-records-77f90d4a-dc7f-4f09-8972-c1b03ea85a67

Step 4 – Wait a while. Or as Spence would say while provisioning your User Profile Application, get a cuppa coffee. DNS sometimes can take a while to provision.

Sadly there are no exciting fireworks through the Azure Portal when you verify ownership of a domain.
Just a quick toast that briefly appears in the upper right hand corner of the Azure Portal.
Step 5 – Determine whether you just want to setup Azure AD Connect to get started with Directory and Password Synchronization, or go back to the Office 365 portal and setup the remaining DNS entries to be able to fully recognize the capabilities of Office 365. Nevertheless, you’ll see this screen within Azure upon completion of domain verification.

Back in the Office 365 Admin Center however, you’ll notice that the domain says that it’s still being setup.
Step 6 – Complete the setup of the domain by clicking on the line item associated with the domain name that has been verified by Microsoft Azure.
If I point my name servers from this domain through my registrar to be managed by Microsoft’s name servers, a lot of things just go away as Microsoft manages the domain for me at that point. If I however want to perform these configurations on my own as I have a complex DNS environment, I can do so by adding the values similar to these (fairly standard where you simply replace “potatoe-cloud” with your DNS name)word:

After you’ve updated your DNS within your registrar, you’ll see something like this if you happen to have an incorrect record…

In my case I accidentally had an extra character in there – simple cut and paste error. 😐
After making my corrections and verifying settings I received a nice note that all was configured and ready to go.

From there, any new user I create within Office 365 will make use of the @potatoe.cloud domain name rather than the Tenant name.
Congrats on having your Office 365 email accounts now masked as well as user login’s. I’d recommend learning how to setup and use Azure AD Connect so that you’re able to move forward with having your domain identities provisioned with Office 365 / Azure Active Directory to enhance your end user’s experience.
Remember – DNS isn’t that difficult. But it’s easy to mess up and also then make things more difficult.