Writing a letter when an employee leaves can be a delicate issue depending on the terms. It is best to be sincere and informal, avoiding any discussion of the reason the employee is leaving.
A letter written to other employees to announce the resignation of one of their colleagues should avoid flowery expressions of sentiment. Instead, the letter should be personal, but not overly familiar. It should comment on the leaving employee's contributions to the company and on any future plans of that employee. If an employee is retiring or leaving to take a position with another company, those facts can be mentioned, but discussion of specific issues behind the separation should be avoided. Any discussion about the employee's age, financial situation or health should also be avoided, as should mention of any conflicts within the workplace.
Individuals within a workplace may also choose to write letters to an employee who is leaving. According to Write Express, these letters should also focus on the positive aspects of the work relationship, even if there has been conflict or if the employee is leaving under a cloud. Congratulating the leaving employee on any future plans and expressing best wishes are always appropriate topics for a leaving letter.