Dear (Recipient’s name)
First Paragraph: I take this opportunity to bid farewell to all of you and wish to inform you that today is my last day at (state the name of your company) as I am leaving my position here. Working in this organisation has been a wonderful learning experience and I will miss you all a lot.
Second Paragraph: I would personally like to thank (state the names of the people who have helped you, or with whom you enjoyed working; you can also name some projects where you worked together) for their constant support and guidance and for making me what I am today.
Third Paragraph: I am looking forward to the new challenges in my career and wish all of you best of luck too. I hope we can be still in touch with each other (give your telephone number and email address).
With regards and best wishes,