COMPLIMENTING SUPPLIER’S EMPLOYEE
I would like you to know how pleased I am of the extra effort taken by [NAME, ex. your salesman, Bill Williams]. [STATE ACTIVITY BEING COMPLIMENTED/THANKED, ex. When our order was delayed due to lack of stock, Bill took it upon himself to arrange for special delivery from your manufacturing plant.]
You are certainly fortunate to have [NAME, ex. Bill] at your firm. We are indeed pleased with [his/her] efforts.