Dear …
I just received the ‘Thank You’ note that you sent to me, thanking me for the __(describe why thanking you)__. Not only am I grateful that you appreciated my efforts, but I also enjoyed doing it for you. It was sure nice of you to extend your gratitude with that note.
You are very important to __(me or company name)__ and it is my pleasure to __(work/deal/etc.)__ with you. __(We or I )__ value your __(business/contributions/etc.)__ and I am here to help you in anyway that I can. When you are happy __(we or I)__ am happy and __(we or I)__ never forget that your success is also __(our/my)__ success.
If there is anything else I can do for you, please don’t hesitate to call me directly. I look forward to having an opportunity to be of service to you again.
Sincerely,