When setting up your account in Office 365, it’s important to consider what you want to name your tenant before you make your account live. “Tenant,” you ask? If you’re not familiar with this term, think of it this way: Office 365 is a multi-tenant cloud, which basically means that the one huge cloud domain (onmicrosoft.com) has many tenants, or clients – kind of like a big apartment building with multiple apartments.
When you create your Office 365 account, you set up your domain, such as contoso.onmicrosoft.com. And here’s the important bit – once you’ve chosen a name, you can’t change it!
According to Technet:
“The name of the tenant appears in Lync invites and SharePoint Online, but Microsoft does not currently have tools to rename a tenant or migrate data from one tenant to another. If you change your mind later, you have to create a new tenant and manually move your data and settings.”
Even though you will add your own domain and use it for Exchange and Lync, whenever you send out a Lync invite it’s going to be coming from thisisjustatrial.onmicrosoft.com (for example). And while you can name your Public SharePoint site to whatever you’d like, your internal SharePoint site is going to be thisisjustatrial.sharepoint.com. Not very pretty, and bound to cause some trouble when users have to try and remember that URL.
So take some time when setting up your tenancy and make sure that your domain name makes sense and isn’t too long or confusing to your users – you’ll be glad you did!