Answer:
The HR department sent this email to explain to employees how the institution handles holidays and how things are done at that institution.
Explanation:
The email was sent to explain to employees how things are done at this institution in relation to the holidays. When the email states that employees should remember that they should talk to managers before filling out the holiday leave form, it is because the HR department wants employees to know how the institution handles holidays. This way, employees can act correctly, without harming the company or themselves.