Exploit of Non-Existent Domain via SPF Bypass

Ibrahim Saud@tektrix

•updated Jun 21, 2026•0•0•2

This rule detects email events where the sender's domain fails basic DNS resolution, indicating it might be non-existent or invalid, but the email successfully bypasses authentication due to SPF macros. This could be an attempt to spoof emails from non-existent domains while still appearing legitimate to email authentication checks.