If your organization is running a local Microsoft Exchange Server e-mail environment, establishing e-mail coexistence allows you to begin using Microsoft Exchange Online with no impact on your existing e-mail system. Some of your users can use Exchange Online, while others continue to use your local Exchange Server environment.
Establishing e-mail coexistence prepares your environment for one-way directory synchronization from your local Active Directory service to Microsoft Online Services. It also prepares your environment for synchronized global address list (GAL) lookup for your e-mail users, regardless of which e-mail environment they are using.
E-mail coexistence requires that your organization be running Exchange 2000 Server, Exchange Server 2003, or Exchange Server 2007 with the latest service packs installed. For information about migrating POP3 and IMAP4 mailboxes to Exchange Online, see POP/IMAP Mail Migration Process.
If your organization has a registered Internet domain that identifies your organization on the Internet, the first step in migrating your local e-mail environment to Exchange Online is to add your domain to Microsoft Online Services. For information about adding your domain to Microsoft Online Services, see About Using Your Domain with Microsoft Online Services.
Enabling e-mail coexistence between your local Exchange Server environment and Exchange Online requires the following steps:
- Add your registered e-mail domain to Microsoft Online Services, and verify that you own it.
- (Optional) Secure the e-mail traffic that is exchanged between your local Exchange Server environment and Microsoft Online Services.
- Enable one-way directory synchronization from your local Active Directory to Microsoft Online Services.
- Install and configure the Microsoft Online Services Directory Synchronization tool.
To perform these steps, launch the Microsoft Online Services Administration Center, and then click the Migration tab. You can reach the E-Mail Coexistence and Directory Synchronization utilities by clicking either of the links under the Migration tab, or the appropriate Configure buttons.
The following features do not work as expected across e-mail environments when operating in e-mail coexistence:
- Mailbox delegation: Users in one e-mail environment cannot assign mailbox management permissions to users in the other e-mail environment.
- Free/Busy information: When scheduling meetings, users in one e-mail environment cannot see the Free-Busy information for users in the other e-mail environment.
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