Tips to help write a farewell message to an employee include to state the reason for the departure and mention some good times or memories. Also, this is not a formal letter, so keep it casual.
Stating the reason for the departure is part of the farewell message, so the writer must address it. Though personal details are not usually necessary, a writer must make sure that there is information indicating that this is a positive, good decision. If personal information is necessary, it should remain as positive as possible.
A writer should also mention any good times or memories from her time with the company, and should not mention negative information. Instead, the writer should remain positive, add humor, and think of one positive event that is always going to remain in her memory. Remember, this letter is for the entire staff, so it must remain appropriate for everyone, even if the writer had a bad experience with another employee.
This is an informal letter and should remain fun, yet sincere. A heartfelt letter is a good gesture, and it also allows the writer a chance to share new contact information, too. Burning bridges with this letter is a bad idea, and writers should make sure that only positive information appears.