For steps on setting up an authentication domain, refer to
"Step 1: Add your sending domain to Postmaster Tools" in the
[Set up Postmaster Tools Help Center article](https://support.google.com/mail/answer/6227174).

## Next step

To set up the Postmaster Tools API, proceed to
[Set up the API](https://developers.google.com/workspace/gmail/postmaster/guides/setup).