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

Why This Matters

Maintaining an approved list of IP addresses for sending mail reduces the risk of unauthorized email relay and spoofing. Without this list, attackers could use unverified IPs to send phishing or spam through your Microsoft 365 tenant, damaging your domain reputation and security posture.

What Aether365 Checks

This check verifies that your Microsoft 365 organization maintains a list of approved IP addresses allowed to send mail. It appears in the Aether365 dashboard under the microsoft-365 checks category, mapped to CIS control CISA.MS.EXO.2.1.