Using Active Directory & Entra ID (Azure AD) for email signatures

Managing email signatures across hundreds or thousands of employees can be tedious for IT. Every role change, new hire, or rebrand means another round of manual updates and support tickets.

For organizations using Office 365 (Microsoft 365) or Microsoft Exchange Server, personalization in email signatures is achieved using Active Directory (AD) or Microsoft Entra ID (formerly Azure AD) to centralize user data. These directories store the key contact details that every email signature depends on.

By connecting directory services like Active Directory or Entra ID with an email signature management platform such as Exclaimer, IT teams can synchronize user attributes directly into email signatures.

What is Active Directory (AD) and Entra ID?

Active Directory (AD) is Microsoft’s long-established on-premises directory service that centralizes authentication, authorization, and user management across a corporate network. It stores and organizes data about users, computers, and groups. This makes it easier for IT teams to enforce access control, apply policies, and maintain consistency across the environment.

Microsoft Entra ID, previously known as Azure Active Directory (Azure AD), is the cloud-based extension of that same identity management framework. It provides secure, scalable identity and access management (IAM) for cloud and hybrid environments. It connects users to Microsoft 365, Exchange Online, and other SaaS applications through single sign-on (SSO) and multi-factor authentication (MFA).

While AD manages identities and attributes locally within your network, Entra ID brings those same identity objects into the cloud. Most modern organizations run a hybrid model, where data from on-prem AD syncs to Entra ID via Microsoft Entra Connect (formerly Azure AD Connect). This keeps user information such as name, title, department, and phone number consistent across both environments.

Using Active Directory for email signatures

For IT administrators, Active Directory (AD) and Entra ID already define the single source of truth for user identity and contact data. Extending that same framework to manage email signatures ensures every message reflects accurate, authenticated information.

In the context of email signatures, Active Directory is used to automatically populate signature templates using one of two common methods:

1. Server-side configuration using mail flow or transport rules: Signatures are appended after an email is sent, typically through Exchange Transport Rules (ETRs). These rules insert HTML templates that reference AD attributes such as displayName, title, or telephoneNumber.

2. Client-side configuration using VBScript: A startup or logon script runs on Windows machines to inject signature templates directly into Outlook’s local signature settings, again pulling data fields from the on-premises AD.

Both methods allow IT to create a level of automation, but they come with trade-offs:

• Mail flow rules offer centralized control but are limited to plain-text disclaimers or static HTML. They lack advanced formatting options, banner placement, and dynamic logic (such as applying different signatures for departments or locations).

• VBScript deployments require ongoing maintenance and permissions. Each device must run the script locally, and any update to the signature template requires re-distribution. This makes scalability difficult in hybrid or remote environments.

These native approaches work, but they’re manual, fragile, and time-consuming. This is especially true when managing large, distributed environments or enforcing compliance standards like GDPR or HIPAA.

Available AD attributes available for email signatures 

When creating Active Directory (AD) or Entra ID (Azure AD)–based email signatures, each signature field is mapped to an attribute stored in the directory. These attributes hold information such as an employee’s name, title, department, or phone number, which can then be inserted into an email signature template automatically.

Using additional Active Directory data in email signatures

If you manage signatures manually through Exchange transport rules or Outlook scripts, you’re limited to the predefined attributes listed above. However, with centralized management tools, you can use additional custom attributes to include unique data points such as certifications, pronouns, or regional compliance statements.

Microsoft Exchange provides 15 Custom (Extension) Attributes—numbered 1 through 15—that can be used to store extra data for email signatures.

Custom attributes can be populated using either:

• The Exchange Admin Center (EAC) under Mailbox Properties → Custom Attributes, or

• The Exchange Management Shell, using a command such as:

Set-Mailbox -Identity "John Smith" -CustomAttribute1 "ISO 27001 Certified"

These custom fields sync automatically when connected to any Entra ID–integrated email signature management platform. This enables advanced personalization and rule-based content logic in your email signature templates.

Common challenges with manual AD signature management

Even with Active Directory (AD) and Entra ID (Azure AD) acting as the backbone for identity management, manually linking that data to email signatures introduces complexity across every layer of IT operations.

In most organizations, signatures are still controlled through a combination of Exchange Transport Rules (ETRs), VBScript deployments, and locally applied Outlook templates. While these methods technically work, they create fragile dependencies that are hard to maintain at scale.

The main challenges include:

• Administrative overhead
  Every time a disclaimer, logo, or layout changes, administrators must modify HTML templates, update transport rules, or redistribute scripts. This often requires elevated permissions on Exchange servers or endpoint management systems.

• Limited feature support
  Native Exchange and Outlook tools don’t support conditional logic, dynamic banners, or attribute-based formatting. They can’t distinguish between departments, subsidiaries, or regions without extensive rule sets or hardcoded templates.

• Attribute synchronization gaps
  In hybrid environments, mismatches between on-prem AD and Entra ID can result in incomplete attribute mapping. Values such as telephoneNumber, physicalDeliveryOfficeName, or extensionAttribute1–15 may fail to populate in signatures if synchronization filters exclude them from Microsoft Entra Connect.

• No centralized visibility or audit trail
  Native tools provide no version history or approval workflow. Compliance teams can’t easily verify which template was active during a given period—an issue for regulated industries that require audit-ready documentation.

• Inconsistent client behavior
  Client-side scripts apply only to Outlook for Windows. Emails sent via Outlook on the web, mobile clients, or third-party mail apps bypass those rules entirely, producing inconsistent signature experiences.

These limitations fragment control, increase administrative risk, and consume valuable engineering time that should be spent on higher-priority security and infrastructure work.

How Exclaimer integrates with Active Directory and Entra ID Data

When integrated with Active Directory or Microsoft Entra ID, Exclaimer automatically synchronizes all available user attributes through secure, read-only connections.

Cloud integration via Microsoft Entra ID

For organizations using Microsoft 365, Exclaimer connects to Microsoft Entra ID through the Microsoft Graph API. This secure, read-only connection allows Exclaimer to retrieve directory attributes such as displayName, title, department, telephoneNumber, and any custom extensionAttribute1–15.

Data synchronization occurs automatically at scheduled intervals. Exclaimer then uses this verified directory data to populate user-specific fields within centralized signature templates.

Signatures are applied server-side via secure connectors in Microsoft 365. This means every email includes the correct branding and contact information before it leaves your organization’s mail flow.

Because data is pulled dynamically from Entra ID, any updates made in Microsoft 365 are reflected across all users’ signatures in near real time. This is without requiring scripts, local installs, or manual reconfiguration.

Hybrid and on-premises integration

In hybrid environments, Exclaimer connects to on-premises Active Directory via a secure LDAP or Azure AD Connect (Entra Connect) configuration. User attributes are synchronized to the Exclaimer cloud using lightweight directory synchronization services, ensuring the same data integrity as a full Entra ID deployment.

This hybrid approach is ideal for organizations that still host Exchange on-premises or operate in regulated industries where certain data must remain within their own infrastructure. Exclaimer’s architecture ensures that:

• User data remains protected in transit through TLS-encrypted channels.

• Directory synchronization is unidirectional (read-only) and does not modify AD or Entra ID objects.

• Attribute mappings mirror Microsoft’s schema definitions, ensuring consistency between environments.

Deployment flexibility

Exclaimer supports both server-side and client-side deployments, depending on policy or mail routing requirements:

• Server-side processing: Signatures are applied after an email is sent, using transport connectors in Microsoft 365 or Exchange. This guarantees full coverage across all devices and mail clients.

• Client-side add-in: The Exclaimer Outlook Add-in (available via AppSource) allows users to preview and switch between approved templates before sending, while still relying on synchronized AD or Entra ID data.

Both deployment models use the same attribute synchronization backbone, ensuring consistency and compliance across your organization’s entire communication stack.

The benefits of using directory-based automation for email signatures

Integrating Active Directory (AD) or Microsoft Entra ID with Exclaimer turns signature management into an automated, governed process that IT can trust. Instead of relying on scripts or static templates, user data flows securely from your directory into standardized layouts—automatically, accurately, and at scale.

Centralized control

Every email signature is managed from one platform. Directory synchronization ensures templates are always current, removing the need for PowerShell commands, VBScript deployments, or manual transport-rule edits.

Reliable consistency

Server-side processing applies the same design across Outlook, web, and mobile clients. Brand updates or layout changes can be deployed globally in minutes, ensuring professional, unified communication without relying on end users.

Policy-driven compliance

Legal disclaimers and regulatory notices can be applied automatically by department, region, or business unit. Role-based access controls (RBAC) and version history provide full visibility for audits and policy reviews.

Security-first integration

Exclaimer connects through Microsoft Graph API or secure LDAP in read-only mode, protecting directory data while keeping it synchronized in real time. Data is encrypted in transit, and Exclaimer’s platform meets ISO 27001 and SOC 2 Type II standards.

Operational efficiency

Directory-based automation eliminates repetitive updates and support tickets. IT retains oversight and governance while reducing time spent managing signatures. This frees up resources for higher-value infrastructure and security initiatives.

The key takeaway

Manual signature management no longer fits the scale or security standards of modern IT environments.

By integrating Active Directory (AD) or Microsoft Entra ID with Exclaimer, IT teams gain centralized control, automation, and full compliance visibility. And all without the complexity of scripts or manual maintenance.

What was once a maintenance burden becomes a controlled, automated workflow that simply works.

Learn more about Exclaimer or get yourself a free trial today.