This subdomain serves the MTA-STS (Mail Transfer Agent Strict Transport Security) policy for Wingu Technology LLC, as defined in RFC 8461.
MTA-STS is a security standard that enables mail service providers to declare their ability to receive Transport Layer Security (TLS) secure SMTP connections and to specify whether sending servers should refuse to deliver email if a secure connection cannot be established.
This implementation helps prevent Man-in-the-Middle (MitM) attacks by enforcing strict certificate validation and ensuring that email transit is encrypted between compliant mail servers.
Technical Reference:
View Active Policy File