Yoda,

I am sorry to learn of your experience.

The letter you describe above is the famous "Better Qualified Applicants" or BQA letter. This is the only written communication that the Secret Service sends to applicants expelled from the process for failing the polygraph.

If you have yet to do so already, I would read the sections on how to appeal your dismissal in The Lie Behind the Lie Detector. Although you will likely have little success in your appeal, you do not want the last thing left in your HQ file to be paperwork describing how you failed the polygraph with no letter of appeal following it. Although the Secret Service is not widely known to share information regarding your failed polygraph with other agencies, it's still not a good idea to let this go uncontested.

The terms “not being within parameters” appear to imply that the second agency you applied with was the FBI. I would file a written appeal here as well.