TMA-M365-DKIM-ENABLED
Ensure DKIM signing is enabled for all Exchange Online domains
Description
DKIM signatures let receivers verify mail really came from your domains and are a prerequisite for an enforcing DMARC policy. Prints the number of domains whose DKIM signing configuration is not enabled (expected 0). 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
$ErrorActionPreference = 'Stop'; if (-not (Get-Command Get-ConnectionInformation -ErrorAction SilentlyContinue) -or -not (Get-ConnectionInformation)) { throw 'Not connected: run Connect-ExchangeOnline first' }; $bad = @(Get-DkimSigningConfig -ErrorAction Stop | Where-Object { $_.Enabled -ne $true }); $bad.Count- Expected output
0
How it is fixed
Fix method: Guidance or infrastructure patch
Publish the selector1/selector2 CNAME records shown by Get-DkimSigningConfig -Identity <domain> | Format-List Selector*CNAME, then New-DkimSigningConfig -DomainName <domain> -Enabled $true or Set-DkimSigningConfig -Identity <domain> -Enabled $true.
Properties
- Operating systems
- Any
- Tags
- m365mail-auth
- Reference
- CIS Microsoft 365 Foundations Benchmark v7.0.0 - Exchange Online / DKIM (verify section number for your release)
Check this host
Run this on a machine you are allowed to audit. The scan is read-only.
tmaegis scan --target m365