Rollout guide
MTA-STS testing versus enforce mode
The right first setting is usually testing. Enforcement is useful only after you have verified every active destination for your email.
Use testing mode when
- You are publishing a policy for the first time.
- You are still confirming your MX hostnames.
- You recently changed mail providers or routing.
Use enforce mode when
- Your MX inventory is complete.
- Your policy is reachable through valid HTTPS.
- You have confirmed normal delivery after testing.