When a company has implemented Exchange hybrid, and has moved some or all their users to Office 365, the question “How do I create a mailbox in Office 365?” frequently comes up.
In this article we explore how to create a mailbox in Exchange Online when directory synchronization is in place. For this article we will explore this process using Exchange 2016. We will look at how to complete this task with the GUI and PowerShell. Note that these steps are identical for Exchange 2013.
Using the Exchange Admin Center
This is the simplest and quickest way to create a mailbox in Office 365. The drawback to this solution is that it only allows you to create an entirely new Active Directory user. A preexisting user without a mailbox can not be enabled for an Office 365 mailbox using the GUI. To grant an existing user an Office 365 mailbox you will need to use PowerShell. Alternatively, that user could be given an on-prem mailbox and then move that mailbox to Office 365.
If your current process is to create a new account in Active Directory first and then enable the mailbox in Exchange second, I would recommend reversing these steps. Using the method below allows you to create a basic user in Active Directory with a mailbox in Office 365. Then you can go back into Active Directory to make any additional changes to the new account, such as group memberships.
For our example, we are going to create a new user called Wilfred Mott who will have a mailbox in Office 365. Wilfred does not currently have a user account in Active Directory so we can use this method. Wilfred’s email will be firstname.lastname@example.org.
From your on-premises Exchange 2016 server, log into the Exchange Admin Center. Select the Recipients tab and Mailboxes sub tab. Click the New (plus sign) and select Office 365 mailbox.
Selecting this option walks you through the process of creating a remote mailbox in Office 365. The benefit here is that you do not need to migrate the mailbox after it is created as it already exists as an object in the cloud. Keep in mind that you will not see this mailbox in the Office 365 tenant until directory synchronization has run. [Read more…] about How to create an Office 365 mailbox (in hybrid)