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 Server 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 Ways to migrate multiple email accounts to Office 365.

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