As you prepare for integration with Office 365, one of the first and most important steps is to ensure you have registered all your User Principal Names (UPNs) and e-mail domains you plan to use with the service. This also includes any e-mail domains you plan to coexist with but will leave on-premises. Let's recap on why both UPNs and e-mail domains are important to register.
A UPN is an individual's log on to Active Directory. In many cases, you are likely to use
domain\%username% as the user log on. We need to change this to their UPN, which is also likely
%username%@domain (in some cases it may be
domain.local or a
public domain.com). We need to ensure your UPN is a public domain. Ideally, we should have the public domain match the user's primary e-mail address.
E-mail domains are also important to register within Office 365. First off, you cannot assign a primary or secondary e-mail address to a mailbox if the e-mail domain is not registered with...