# UPN suffixes count should be retrievable

UPN (User Principal Name) suffixes are a critical component of Active Directory authentication infrastructure.

Source: https://maester.dev/docs/tests/AD-FORS-01

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<div class="test-byline"><div class="test-byline-avatars"><a class="test-byline-avatar test-byline-avatar--author" href="/contributors/soulemike" title="Michael Soule · Original author"><img src="https://github.com/soulemike.png" alt="Michael Soule" width="28" height="28" loading="lazy" decoding="async" /></a></div><div class="test-byline-meta"><span class="test-byline-text">Contributed by <a href="/contributors/soulemike">Michael Soule</a></span><a class="test-byline-link" href="/contributors">All contributors →</a></div></div>

<p class="test-part">Part of <a href="/docs/tests/ad">Active Directory</a> · Active Directory · Domain and forest · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-FORS-01
```

## Overview

UPN (User Principal Name) suffixes are a critical component of Active Directory authentication infrastructure. They allow users to log on using an email-style username format (user@suffix) rather than the traditional domain\username format. Understanding the UPN suffix configuration is important for:

- **Authentication Experience**: UPN suffixes enable a consistent logon experience across multiple domains and forests
- **Identity Management**: During mergers and acquisitions, UPN suffixes help maintain brand identity while consolidating directories
- **Security Assessment**: Unnecessary or unauthorized UPN suffixes could indicate misconfiguration or security risks
- **Compliance**: Some compliance frameworks require visibility into all authentication namespaces

#### Control Type

**Operational**

#### Security Recommendation

Regularly review configured UPN suffixes to ensure:
- Only legitimate organizational domains are configured as UPN suffixes
- Unused or deprecated UPN suffixes from past mergers are removed
- UPN suffixes align with the organization's current domain and brand strategy

#### How the Test Works

This test retrieves the UPN suffixes configured at the forest level using the `Get-ADForest` cmdlet. It counts the number of custom UPN suffixes and reports whether any are configured. The default forest domain is not counted as a custom suffix.

#### Related Tests

- `Test-MtAdUpnSuffixesDetails` - Provides detailed list of all configured UPN suffixes
- `Test-MtAdSpnSuffixesCount` - Checks SPN suffix configuration for service principal management

## Details

<details>
<summary>Every attribute of this check</summary>

| Field | Value |
| --- | --- |
| Test ID | AD-FORS-01 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Domain and forest |
| Area | Infrastructure hardening |
| Resource type | Tenant |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdUpnSuffixesCount](https://github.com/maester365/maester/blob/main/tests/ad/domain/Test.AD-FORS-01.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:crossRef:ReadProperty |

</details>

## Source

- Test: [`tests/ad/domain/Test.AD-FORS-01.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/domain/Test.AD-FORS-01.ps1)
- Documentation: [`tests/ad/domain/Test.AD-FORS-01.md`](https://github.com/maester365/maester/blob/main/tests/ad/domain/Test.AD-FORS-01.md)