Good Luck/Goodbye with Thanks
I was very happy for you when I heard that you were taking a new position in __(name of branch/dep’t/city/country)__. It sounds like a wonderful opportunity for you and I just can’t think of anyone who is more deserving. They definitely chose the right person!
You have given me so much support and encouragement since I have been with this __(compay/organization)__ and I wanted to take this opportunity to let you know just how much I have appreciated it. Thank you for everthing, __(name)__, it meant a lot to me. You will be greatly missed by so many people here, but you will especially be missed by me.
I know that you will do great in your new job and I am genuinely delighted for you. Please try to keep in touch with us now and again. Farewell, __(name)__. I wish you nothing but the very best of luck in your new venture!