Most Office 365 plans include the same features for domains. For example, you can add multiple custom domains, add subdomains, and decide whether you want to manage DNS for a custom domain yourself or have Office 365 manage DNS for the domain.
Review the information below to understand how you can use Office 365 in your organization. The Office 365 domains service description includes an even more detailed list. You can also review the overall product features of each offering.
You can add additional domains. For example, you could add the domains contososolutions.com and contosomarketing.com after setting up your first domain. How? You can add additional domains to Office 365 with the domains wizard.
You can add multiple domains or subdomains. For example, you could add the domains contoso.com and contosomarketing.com, and then add the subdomains www.contoso.com, www.partners.contoso.com, www.partners.marketing.contoso.com, and so on. How? You add additional domains or subdomains the same way you added your initial custom domain, by following the steps in the domains setup wizard.
When you add multiple domains to Office 365, you can host any of the services (like email) on any of the domains you've added. When you change your email to Office 365, by updating a domain's MX record, ALL email sent to that domain will start coming to Office 365. Alternatively, you can take steps to pilot Office 365 with just a few email addresses instead.
If you already have a public website that you use with your domain, when you add your domain to Office 365, you can keep hosting your current website where it is hosted now without taking extra steps.
How? When you set up your domain in Office 365, in the domains setup wizard, be sure to choose Yes when asked if you have a website you're already using. (Or choose the option to manage your own DNS records.) Then you add and update your DNS records on your DNS host website to configure the DNS records for services, such as email and Skype for Business Online. Setting up these services does not affect your website.
Choose how you'll manage DNS for your domain. You can continue to manage your DNS records at your DNS hosting provider (or on premises, if you manage your own DNS file locally)—for example, to add or update MX or CNAME records. Or you can have Office 365 set up and manage DNS records for your domain. You'll have the option to choose how to manage DNS records when you step through the domains setup wizard.
If you choose to have Office 365 create and host your domain's DNS records, email and IM are automatically set up to use your domain, hosted by Office 365, and you can’t host email or IM with another hosting provider. You also cannot add a subdomain of your domain unless you first change DNS management to a DNS host outside Office 365 for your domain.
If you choose to manage DNS for your domain yourself, you can set up email, IM, and your public website to use your domain in Office 365, or you can host some (or all) of those services on your domain with another provider.
Note: If you're adding a subdomain, like sales.contoso.com, you must manage DNS for the domain outside of Office 365. Also, if GoDaddy is your domain registrar, you cannot have Office 365 manage your domain.
More about how domains work with Office 365 services
Typically, you can add up to 900 domains to your Office 365 subscription. Under the following circumstances, the limit might be lower:
Skype for Business Online has a limit of 600 SIP domains. While you still can add up to 900 domains to Office 365, only 600 SIP domains will be available for use with Skype for Business Online.
The following scenario is unlikely, but good to keep in mind if you have a large number of Office 365 domains. Verified domains are stored as tenant-specific information, and there is currently a limitation as to how much tenant-specific information Office 365 can store for a given tenant. Using various Office 365 features can contribute to this limit and prevent you from adding 900 verified domains to your tenant.
If this describes your situation, and you try to add more domains but get an error, contact Microsoft Support to learn if you are running into this limitation.
If you are in China, and using Office 365 operated by 21Vianet, see Get technical, billing, and subscription support for Office 365 operated by 21Vianet.
Office 365 creates a domain for you when you sign up with the service, like contoso.onmicrosoft.com. You can keep using this domain for your user ID and for your Office 365 services, or add your own custom domain.
You can use any custom domain name that is available at your domain name registrar. It doesn’t have to match the first part of your onmicrosoft.com domain. For example, if you signed up for Office 365 using fabrikam.onmicrosoft.com, you could use fabrikam.com, fabrikam_NW.com, or a completely different name like fourthcoffee.com.
Learn more at Get help with Office 365 domains.