Session request from unauthorized senders must be rejected.
Sender Identification (SID) is an email anti-spam sanitization process. Sender ID uses DNS MX record lookups to verify the SMTP sending server is authorized to send email for the originating domain.
Failure to implement Sender ID risks that SPAM could be admitted into the email domain that originates from rogue servers. Most SPAM content originates from domains where the IP address has been spoofed prior to sending, thereby avoiding detection.
By rejecting session initiations from senders who cannot be validated via Sender ID, potential SPAM is eliminated because it is evaluated prior to being admitted to the domain.