Hi [candidate],
After careful consideration of your application, we have decided to select a candidate who we believe best matches our needs.
I want to personally thank you for applying to work at [company]. Your application made an impact on us and we appreciate your interest in our company.
As a transparent organization, we want to provide you with some feedback on our decision: [feedback]
Lastly, we would like to keep your application and contact information on file in case a future opportunity arises. Is this okay with you?
We wish you the best of luck in your future endeavors.
Sincerely,
[Your signature]