Understanding Cloud-Only Deployments

A cloud-only deployment is one where your Exchange Online email organization isn’t connected with your on-premises directory and Exchange organization in a hybrid deployment. Exchange Online is the cloud-based email service that is part of Microsoft Office 365. A cloud-only deployment is most often used when you want to migrate all mailboxes from your existing on-premises Exchange organization to Exchange Online, and eventually decommission your on-premises email system. Following are some characteristics of a cloud-only deployment:

• If you have an on-premises Exchange organization, the Exchange Online organization looks like an external mail system.
  
• If you maintain your on-premises Exchange organization, users need to use different credentials to access their Exchange Online mailboxes.
  
• Your on-premises directory isn't synchronized with the Office 365 organization. Exchange Online mailboxes and distribution groups are managed separately from on-premises mailboxes and distribution groups.
  

If you've already signed up for Office 365, click Cloud Only in the Exchange 2013 Deployment Assistant and answer a few questions about your current environment. Then, the Deployment Assistant will determine the best option to migrate on-premises mailboxes to Exchange Online. To learn more about the options you can use to migrate mailboxes to Exchange Online, see Mailbox Migration to Exchange Online.

If the cloud-only option doesn't support your existing Exchange deployment or your organization's needs, you have to implement a hybrid deployment between your on-premises Exchange organization and your Exchange Online organization in Office 365. With a hybrid deployment, you get the following capabilities:

• Directory synchronization between your on-premises and Exchange Online organizations.
  
• Single sign-on to mailboxes located either on-premises or in the Exchange Online organization.
  
• Secure mail routing between on-premises and Exchange Online organizations.
  
• Free/busy and calendar sharing between on-premises and Exchange Online organizations.
  
• And more.
  

To learn more about hybrid deployments, see Exchange Server 2013 Hybrid Deployments. Or, click Hybrid in the Exchange 2013 Deployment Assistant, answer a few questions about your current environment, and the Deployment Assistant will generate a list of hybrid deployment instructions for you.