CISA.MS.EXO.5.1 - SMTP AUTH SHALL be disabled.

Overview

SMTP AUTH SHALL be disabled.

Rationale: SMTP AUTH is not used or needed by modern email clients. Therefore, disabling it as the global default conforms to the principle of least functionality.

Remediation action:

1. To disable SMTP AUTH for the organization:
2. Sign in to the Exchange admin center.
3. On the left hand pane, select Settings; then from the settings list, select Mail Flow.
4. Make sure the setting Turn off SMTP AUTH protocol for your organization is checked.

Related links

• Exchange admin center - Settings
• CISA 5 Simple Mail Transfer Protocol Authentication - MS.EXO.5.1v1
• CISA ScubaGear Rego Reference

Test Metadata

Field	Value
Test ID	CISA.MS.EXO.5.1
Severity	High
Suite	CISA
Category	exchange
PowerShell test	Test-MtCisaSmtpAuthentication
Tags	CISA, CISA.MS.EXO.5.1, MS.EXO, MS.EXO.5.1

Source

• Pester test: tests/cisa/exchange/Test-MtCisaSmtpAuthentication.Tests.ps1
• PowerShell source: powershell/public/cisa/exchange/Test-MtCisaSmtpAuthentication.ps1