You can create a new user mailbox from scratch in Microsoft Exchange Server 2016 or you can create a user mailbox from existing user account in an active directory domain. When you create a mailbox from an existing account, their information is pulled from active directory domain. When you create a new user in Exchange Server 2016 and provide complete detail, it's user account is already created in active directory domain.
In this article, we will look into the method of creating a new user mailbox in Exchange Server 2016 by providing details.
Create a New User Mailbox in Microsoft Exchange Server
1. Log in to Exchange Admin Center (EAC) with administrator account on following URL,
https://<Exchange Server FQDN>/ecp
2. In mailboxes tab, click plus sign -> User mailbox
3. Choose new user, type first name, last name, type the user's alias in user logon name, type password and confirm password, and click Save. The newly created user will be added in Users container in active directory.