# A list of approved IP addresses for sending mail SHALL be maintained

This test is deprecated by CISA as of May 2024 and will always be skipped.

Source: https://maester.dev/docs/tests/CISA.MS.EXO.2.1

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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><a class="test-byline-avatar" href="/contributors/weycc81" title="Stefan Wey · Co-contributor"><img src="https://github.com/weyCC81.png" alt="Stefan Wey" width="28" height="28" loading="lazy" decoding="async" /></a><a class="test-byline-avatar" href="/contributors/samerde" title="Sam Erde · Co-contributor"><img src="https://github.com/SamErde.png" alt="Sam Erde" 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> with 2 co-contributors</span><a class="test-byline-link" href="/contributors">All contributors →</a></div></div>

<p class="test-part">Part of <a href="/docs/tests/cisa">CISA</a> · Exchange Online · Email authentication · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId CISA.MS.EXO.2.1
```

## Overview

**This test is deprecated by CISA as of May 2024 and will always be skipped. The content below is retained as a historical archive and will be removed in a future version.**

MS.EXO.2.1v1 was removed because it is not a security configuration that can be audited; it acts as an implementation step for MS.EXO.2.2. Maintaining the list of approved IP addresses has been incorporated into the implementation guidance for MS.EXO.2.2 and removed as a standalone policy. See [CISA SCuBA Removed Policies — MS.EXO.2.1v1](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/baselines/removedpolicies.md#msexo21v1).

A list of approved IP addresses for sending mail SHALL be maintained.

Rationale: Failing to maintain an accurate list of authorized IP addresses may result in spoofed email messages or failure to deliver legitimate messages when SPF is enabled. Maintaining such a list helps ensure that unauthorized servers sending spoofed messages can be detected, and permits message delivery from legitimate senders.

#### Remediation action

* Identify any approved senders specific to your agency.
* Perform regular review of SPF record and update as necessary.
* Additionally, see [External DNS records required for SPF](https://learn.microsoft.com/microsoft-365/enterprise/external-domain-name-system-records?view=o365-worldwide#external-dns-records-required-for-spf) for inclusions required for Microsoft to send email on behalf of your domain.

#### Related links

* [Exchange admin center - Accepted domains](https://admin.exchange.microsoft.com/#/accepteddomains)
* [CISA 2 Sender Policy Framework - MS.EXO.2.1v1](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/baselines/exo.md#msexo21v1)
* [CISA ScubaGear Rego Reference](https://github.com/cisagov/ScubaGear/blob/main/PowerShell/ScubaGear/Rego/EXOConfig.rego#L58)

## Details

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

| Field | Value |
| --- | --- |
| Test ID | CISA.MS.EXO.2.1 |
| Severity | Medium |
| Suite | CISA |
| Product | Exchange Online |
| Feature | Email authentication |
| Area | Email and collaboration protection |
| Resource type | Domain |
| User impact | Low |
| Implementation cost | Medium |
| MITRE ATT&CK | T1684.002 Email Spoofing |
| Supports benchmark | CISA SCuBA Secure Configuration Baselines for Microsoft 365 (version ScubaGear main, 2026-10-11), requirement MS.EXO.2.1 |
| Criticality | SHALL |
| Supports controls | cisa-scuba:MS.EXO.2.1 |
| PowerShell test | [Test-MtCisaSpfRestriction](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.2.1.ps1) |
| Services | Graph |
| Lifecycle | Deprecated |

</details>

## Source

- Test: [`tests/cisa/exchange/Test.CISA.MS.EXO.2.1.ps1`](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.2.1.ps1)
- Documentation: [`tests/cisa/exchange/Test.CISA.MS.EXO.2.1.md`](https://github.com/maester365/maester/blob/main/tests/cisa/exchange/Test.CISA.MS.EXO.2.1.md)