Microsoft 365
TMA-M365-SMTP-AUTH-DISABLED
Ensure SMTP AUTH client submission is disabled organization-wide
HighLevel 1Automatedm365
Description
SMTP AUTH uses basic authentication and bypasses MFA; it should be disabled tenant-wide and enabled only per mailbox where unavoidable. Requires an already-connected Exchange Online session: Install-Module ExchangeOnlineManagement; Connect-ExchangeOnline (View-Only Organization Management is sufficient). The audit throws if no session exists.
How it is checked
Audit method: Shell command
shell
$ErrorActionPreference = 'Stop'; if (-not (Get-Command Get-ConnectionInformation -ErrorAction SilentlyContinue) -or -not (Get-ConnectionInformation)) { throw 'Not connected: run Connect-ExchangeOnline first' }; $t = Get-TransportConfig -ErrorAction Stop; if ($t.SmtpClientAuthenticationDisabled -eq $true) { 'compliant' } else { 'noncompliant' }- Expected output
compliant
How it is fixed
Fix method: Guidance or infrastructure patch
Set-TransportConfig -SmtpClientAuthenticationDisabled $true (re-enable for individual devices with Set-CASMailbox <mbx> -SmtpClientAuthenticationDisabled $false).
Properties
- Operating systems
- Any
- Tags
- m365authentication
- Reference
- CIS Microsoft 365 Foundations Benchmark v7.0.0 - Exchange Online / SMTP AUTH (verify section number for your release)
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
shell
tmaegis scan --target m365