This e-mail is to thank an interviewer after you have had a job interview. It's a simple bit of courtesy that works wonders.
I just wanted to drop you a message to thank you for the job interview <interview date or day>. I enjoyed speaking with you and I hope you found the time productive as well. If you have further questions or would like to contact me for another meeting, please send me a reply e-mail or simply give me a call. I hope to hear from you soon, and thanks again for considering me for the position of <available position>.