Exchange Server 2013 administration overview : Exchange Server and Active Directory, Exchange Online and Office 365

Exchange stores four types of data in Active Directory: schema data (stored in the Schema partition), configuration data (stored in the Configuration partition), domain data (stored in the Domain partition), and application data (stored in application-specific partitions). In Active Directory, schema rules determine what types of objects are available and what attributes those objects have. When you install the first Exchange server in the forest, the Active Directory preparation process adds many Exchange-specific object classes and attributes to the Schema partition in Active Directory. This allows Exchange-specific objects, such as agents and connectors, to be created. It also allows you to extend existing objects, such as users and groups, with new attributes, such as attributes that allow user objects to be used for sending and receiving email. Every domain controller and global catalog server in the organization has a complete copy of the Schema partition.

During the installation of the first Exchange server in the forest, Exchange configuration information is generated and stored in Active Directory. Exchange configuration information, like other configuration information, is also stored in the Configuration partition. For Active Directory, the configuration information describes the structure of the directory, and the Configuration container includes all of the domains, trees, and forests, as well as the locations of domain controllers and global catalogs. For Exchange, the configuration information is used to describe the structure of the Exchange organization. The Configuration container includes lists of templates, policies, and other global organization–level details. Every domain controller and global catalog server in the organization has a complete copy of the Configuration partition.

In Active Directory, the Domain partition stores domain-specific objects, such as users and groups, and the stored values of attributes associated with those objects. As you create, modify, or delete objects, Exchange stores the details about those objects in the Domain partition. During the installation of the first Exchange server in the forest, Exchange objects are created in the current domain. Whenever you create new recipients or modify Exchange details, the related changes are reflected in the Domain partition as well. Every domain controller has a complete copy of the Domain partition for the domain for which it is authoritative. Every global catalog server in the forest maintains information about a subset of every Domain partition in the forest.

Within the organization, the Transport service on Mailbox servers uses the information about sites stored in Active Directory to determine how to route messages, and these servers can also route messages across site links. They do this by querying Active Directory about its site membership and the site membership of other servers, and then using the information they discover to route messages appropriately. Because of this, when you are deploying an Exchange Server 2013 organization, no additional configuration is required to establish routing in the Active Directory forest.

For mail delivery within the organization, additional routing configuration is necessary only in these specific scenarios:

You can use two types of Mail Transport servers: Mailbox servers and legacy Edge Transport servers. You deploy Mailbox servers within the organization. The Transport service on Mailbox servers handles mail delivery and receipt of mail. Two new services are used to deliver mail items to and receive mail items from other servers:

With Mailbox servers as your transports, no other special configuration is needed for message routing to external destinations. You must configure only the standard mail setup, which includes identifying DNS servers to use for lookups. With legacy Edge Transport servers, you can optimize mail routing and delivery by configuring one-way synchronization from the internal Mailbox servers to the perimeter network’s Edge Transport servers. Beyond this, no other special configuration is required for mail routing and delivery.

You deploy legacy Edge Transport servers in the organization’s perimeter network for added security. Typically a perimeter network is a secure network set up outside the organization’s private network. When you have Edge Transport servers, mail items from outside the organization are received first by the Edge transport servers, which can perform anti-malware and anti-spam checks before passing along mail items to internal Mailbox servers for delivery. Mail items for submission outside the organization are passed from internal Mailbox servers to Edge Transport servers which then submit the mail items for delivery outside the organization.

Exchange Online and Office 365

Exchange Online is a cloud-based service from Microsoft that allows you to implement an online or hybrid implementation of Exchange. Although Exchange Online can be your only solution for all your enterprise messaging needs, a hybrid implementation gives you an integrated online and on-premises solution.

You can get Exchange Online as a standalone service or as part of an Office 365 plan. Currently, Microsoft offers several Exchange Online plans, including a basic plan and an advanced plan. The key differences between the basic and advanced plans are the inclusion of in-place hold and data loss prevention options that may be needed to meet compliance and regulatory requirements. Both plans support Active Directory integration for single sign-on, synchronization with your on-premises Active Directory infrastructure, and creation of hybrid Exchange organizations.

Microsoft offers a variety of Office 365 plans. Some of these plans include access to Office Web Apps, the full desktop versions of Office, or both, as well as access to Exchange Online. You’ll likely want to use an Office 365 midsize business or enterprise plan. These plans include Active Directory integration, which is required if you want to create a hybrid Exchange organization.