GAL Sync (Global Address List)

The Global Address List (GAL) is the directory of all mail-enabled users, groups, and contacts in a Microsoft Exchange or Microsoft 365 organization. GAL sync for email signatures pulls fields like displayName, jobTitle, department, telephoneNumber, mobilePhone, physicalDeliveryOfficeName, and thumbnailPhoto from the GAL into signature templates. In Microsoft 365 environments, the GAL is exposed through the Microsoft Graph API and Exchange Online directory services, which is what signature management platforms query during sync. GAL sync is essentially the Microsoft-native form of directory sync, distinct from custom attribute systems because the data is governed by Exchange admin policies, change tracked, and consistent across Outlook, Teams, and Microsoft 365 services. When a signature platform uses GAL sync correctly, the same source of truth used for Outlook's address autocomplete drives the email signature, eliminating data divergence between identity systems and signatures.