Hybrid CloudsConnecting the cloud to your on-premise systems |
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Understanding Coexistence Coexistence offers organizations the ability to extend the feature-rich experience and administrative control they have with their existing on-premises Microsoft Exchange organization to the cloud. |
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Coexistence provides the seamless look and feel of a single Exchange organization between an on-premises organization and a cloud-based organization. In addition, coexistence can serve as an intermediate step to moving completely to a cloud-based Exchange organization. For larger client it may not be feasible to move all of your users into Office 365, or it may be you want to leverage the cloud for your archives but keep your mailboxes on premise.
Types of Coexistence
A coexistence deployment can be either limited, simple or rich:
- Limited coexistence is where all user email will be moved to the cloud and there will be no on premise email systems, but you still want to connect to your on premise Active Directory for Single Sign On.
- Simple coexistence is usually only used during migrations and offers singly sign on plus only basic email features of a unified global address list (GAL) and mail routing between the on-premises and cloud-based organizations.
- Rich coexistence offers the features of simple coexistence plus additional messaging features typically available in an on-premises Exchange deployment, including sharing free/busy and calendar information between the organizations and the ability to move mailboxes from the on-premises organization to the cloud-based organization.
Feature |
Limited |
Simple coexistence |
Rich coexistence |
Single Sign On for Users (ADFS) |
Yes |
Yes |
Yes |
Mail routing between on-premises and cloud-based organizations |
No |
Yes |
Yes |
Mail routing with a shared domain namespace (both organizations use @contoso.com SMTP domain) |
No |
Yes |
Yes |
Unified GAL (Via DirSync) |
No |
Yes |
Yes |
Free/busy and calendar sharing between on-premises and cloud-based organizations |
No |
No |
Yes |
Centralized mail flow control; the on-premises organization can control mail flow for both organizations |
No |
No |
Yes |
Single Outlook Web App URL for both the on-premises and cloud-based organizations |
No |
No |
Yes |
Move existing on-premises mailboxes to the cloud-based organization |
No |
No |
Yes |
Centralized mailbox administration using the on-premises Exchange Management Console (EMC) |
No |
No |
Yes |
Message tracking, MailTips, and multi-mailbox search between on-premises and cloud-based organizations |
No |
No |
Yes |
Coexistence Components
Deploying coexistence involves several different services and components:
- Microsoft Office 365: The Office 365 service provides a cloud-based Exchange organization as a part of its subscription service. Organizations deploying coexistence must create and configure this cloud-based Exchange organization.
- Coexistence Server: A coexistence server is an Exchange Server 2010 server that is installed in your existing Exchange organization, and it's required for coexistence deployments. It enables messaging features and messaging delivery between your existing Exchange organization and the Office 365-based Exchange organization.
- Microsoft Federation Gateway: The Microsoft Federation Gateway is a cloud-based service offered by Microsoft that acts as the trust broker between your on-premises Exchange 2010 organization and the cloud-based Exchange organization. Organizations deploying rich coexistence must create a federation trust with the gateway. Learn more at: Microsoft Federation Gateway
- Active Directory Synchronization (DirSync): DirSync replicates on-premises Active Directory information for mail-enabled objects to the cloud-based organization to support the unified GAL. Organizations deploying coexistence must deploy DirSync on a separate, on-premises server.
See our FAQ section for explanations any other acronyms or components.
Next Steps ...
- Read about the 5 tiers of Migration Services Parative offer for Office 365
- Book Parative to come in and connect you to the cloud
- Book to see a demo of the Office 365 features in action
- Sign up to a trial of Office 365 right now. Free for 30 days for 25 users. Test it for yourself and see how good the cloud is