It’s with mixed emotions that I write to you today. As many of you have heard, I will be leaving ________________ at the end of next week. Although I greatly enjoy working for this company, and with all of you, an opportunity has arisen that I could not easily turn down. Thank you so much for your support and friendship over these past years. I am grateful for having had the chance to work with such an incredible group of people.
(YOUR NAME HERE)