mta-sts/mta-sts.md

Example: mta-sts.txt

This is an example of an MTA-STS policy file with all possible values.
Save this file as .well-known/mta-sts.txt and serve it over HTTPS at:
https://mta-sts.example/.well-known/mta-sts.txt

---

Policy Fields

version: STSv1
# The version of the MTA-STS policy. Must be "STSv1".

mode: enforce
# The policy mode. Possible values:
#   enforce   - SMTP servers must enforce the policy.
#   testing   - Policy is in testing; violations are reported but not enforced.
#   none      - No policy is applied.

mx: mail.example.com
mx: *.mail.example.net
# The list of MX patterns (hostnames) that are valid for your domain.
# Wildcards (*) are allowed only as the left-most label.

max_age: 86400
# The time (in seconds) that the policy is valid for.
# Recommended minimum is 86400 (1 day). Maximum is 31557600 (1 year).

---

Example Full Policy

version: STSv1
mode: enforce
mx: mail.example.com
mx: *.mail.example.net
max_age: 86400

---

For more details, see:
https://datatracker.ietf.org/doc/html/rfc8461