Yes. This could be the shortest article I have ever written!
Here is what to write..
1. Make sure you cc in any agent you are working through so they know what has been said.. The firm may think you are trying to circumnavigate their involvement..
2. Thank the interviewer for their time and say what a pleasure it was meeting them. Write a note explaining what it was you particularly enjoyed:- the location, the firm, the people, the role etc..
3. Give a quick sentence or two on the benefits of them employing you or using your services. If you thought anything was missed out of interview include it here.
4. If you have a reference the employer can speak to prior to making an offer you could put them forward (ensure you check with the reference).
5. If salary was discussed but not definitive in scope, expand a bit on what you are looking for. The firm may have got the wrong end of the stick during interview
The major failing we often see in emails after interview is candidates who take the opportunity to highlight a negative issue and try to explain it further. This is a definite no-no. For example – “I know in interview that I said I was looking to work full time but I would have to drop my daughter off at school before coming into work so may be a bit late some days. I hope this won’t cause too much inconvenience.” Avoid at all costs!