Take care when naming your Office 365 tenant

When signing up for Office 365 there are two really important decisions:

  1. Where will my tenant be homed (based on the region selected at sign-up)?
  2. What will my tenant be called?

The reason these are so important is because, once set, they cannot be changed.

I’ll write more about the home location of the tenant in a future post (why it matters in some ways, and why it doesn’t in others) but, for now, let’s look at the tenant name.

To explain what this is, when you sign up for Office 365, a new tenant is created and given a name in the form tenantname.onmicrosoft.com.

By default, users log on with username@tenantname.onmicrosoft.com and that becomes their email address too. Other domain names can be added to the tenant (I have markwilson.onmicrosoft.com but I’ve also associated the markwilson.co.uk, markwilson.it, wilsonfamily.org.uk and several other domain names with the tenant) after which the user name can be changed accordingly, as well as the email addresses. The initial tenantname.onmicrosoft.com name can’t be removed though.

Indeed, the only time you’ll see the tenant name is in the URIs for SharePoint Online and OneDrive for Business which are tenantname.sharepoint.com and tenantname-my.sharepoint.com respectively.

Pick your name carefully. What seems a good idea today may not seem so good further down the road. I recently worked with a customer who now regrets the NT domain name used for their Active Directory being named after the town where they are based but it’s too risky to change it now. Similarly your Office 365 tenant name (which is actually your Microsoft Online Services tenant name) needs to be chosen with care. Personally, I’d avoid putting 365 in it as the scope is potentially much broader. companyname.onmicrosoft.com is probably about the safest bet, at least until your company merges with another company! Or you could go with something completely ambiguous like ABC123…

Further reading

About your initial onmicrosoft.com domain in Office 365.

5 thoughts on “Take care when naming your Office 365 tenant


  1. Hi Mark,

    I must be missing something because I can’t see where I choose my tenant name when signing up to O365.

    I have actually gone through the Azure account setup as we plan to user AD Connect to sync users and use other Azure services.

    This setup is in three parts; Name & company, contact details, then billing details. My sign in email address was (I am making this up) companygroupadmin@outlook.com

    After completing the rest of the sign-up process my tenant was created automatically as companygroupoutlook.onmicrosoft.com

    There was no field to enter a tenant name, or chose what it should be. Can you explain where in the sign up process the name is chosen?

    Many thanks
    Great blog by the way.


  2. Hi Michael, it’s been a while since I created a tenant so maybe the process has changed. It could also be different in your case as you already had a Microsoft Online tenant created for Azure.

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