Address books in Exchange Online

Exchange Online uses address books to organize and store email address information for recipients in the organization. The topics that will help you learn about and configure email addresses and address books in Exchange Online are described in the following table.

Key terminology Description Topic
Address book policies The global address list (GAL) is the master list of all recipients in your Exchange Online organization. Address book policies (ABPs) provide a simpler mechanism for GAL segmentation in organizations that require multiple GALs. An ABP defines a GAL, an offline address book (OAB), a room list, and one or more address lists. You can then assign the ABP to users. Address book policies in Exchange Online
Address lists An address list is a subset of a GAL. Each address list is a dynamic collection of one or more types recipients. You can use address lists to help users find the recipients and resources that they need. Address lists
Hierarchical address books The hierarchical address book (HAB) presents recipients in the GAL by using your organization's unique business structure (for example, seniority or management hierarchy), which provides an efficient method for locating internal recipients. Hierarchical address books
Offline address books An offline address book (OAB) is a collection of address lists that can be downloaded and used in Outlook by users that are disconnected from the Exchange Online organization. Offline address books in Exchange Online

Note: Email address policies are available in Exchange Online, but only for Microsoft 365 groups. For more information, see Choose the domain to use when creating Microsoft 365 Groups.

For help with everyday email tasks, such as organizing your contacts in Outlook, check the Office 365 Learning Center. You can find help including: