Can I add custom subdomains or multiple domains to Office 365?

Most Office 365 operated by 21Vianet 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.

  • You can add multiple subdomains. For example,,,, and so on.

  • 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.

    Set up your domain in Office 365, and in the domains setup wizard, be sure to choose Yes when asked if you have a website you're already using. Then you add and update your DNS records on your DNS hosting provider website to configure the DNS records for services, such as email and Lync.

  • 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 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.

    If you choose to manage DNS for your domain yourself, you can set up email, IM, and your public website to use your domain hosted by Office 365, or you can host some (or all) of those services on your domain with another provider.

  • You can add multiple domains to Office 365, and you can host any of the services on any of the domains.

More about how domains work with Office 365 services

  • In most circumstances, you can add up to 900 domains to your Office 365 subscription. If you're planning to use many domains, see Using a large number of domains with Office 365.

  • Office 365 creates a domain for you when you sign up with the service, like 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 domain. For example, if you signed up for Office 365 using, you could use,, or a completely different name like

Learn more at Get help with Office 365 domains.

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