After you set up your custom domain in Office 365 (like fourthcoffee.com, for example), you can change the default domain used for new email addresses when you add users in Office 365 Small Business or add users in Office 365 Enterprise or Office 365 Midsize Business.
To change the default domain:
- Go to the domain manager page by doing one of the following:
- If you’re using Office 365 Small Business, on the Manage your organization page, choose Manage your domains for website and email.
- Otherwise, choose Admin > Office 365, and then, on the left, choose Domains.
- Choose a domain, and then, on the right, click Set as default.
- In an earlier Microsoft cloud service, BPOS, there was also a concept of a primary domain, which was also the default domain. Office 365 does not have primary domains.
- If you use other Microsoft cloud services, such as CRM or Azure, you don’t need to add your domain to each service. Sign up for one of the services and add your domain, and you can use the same sign-in credentials and domain with all the services.