Not having a published or updated policy file for your domain can be the primary reason for coming across error messages like “MTA-STS policy is missing: STSFetchResult.NONE”, implying that the sender’s server couldn’t fetch the MTA-STS policy file when it queried the receiver’s DNS,...
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MTA-STS uses DNS TXT records for policy discovery. It fetches the MTA-STS policy from an HTTPS host. During the TLS handshake, initiated to fetch a new or updated policy from the Policy Host, the HTTPS server must present a valid X.509 certificate for the "MTA-STS" D...
policy, as a change in the id signals to senders that they need to re-fetch the policy. The id doesn't need to be globally unique, don’t worry about other domain owner’s policy id’s. After any MTA-STS policy updates, you need to update the id, or senders will keep using ...
The MTA-STSprotocolis implemented by having a DNS record that specifies that a mail server can fetch a policy file from a defined subdomain. This policy will then be fetched via HTTPS, authenticated and list the names of the recipients' mail servers. These names are also authenticated wit...
Furthermore, MTAs fetch and store MTA-STS policy files, which securely serve the MX addresses making it more difficult for attackers to launch a DNS spoofing attack. MTA-STS offers protection against: Downgrade attacks Man-In-The-Middle (MITM) attacks ...