Letter Of Displeasure On Using Foul Language In Emails

I have to draft a letter of displeasure for using foul language in official emails. Please help with the content of letter
The employee has been on unauthorized leave for long. Now during the inquiry process he has used foul language in his emails to HRD

Instead of sending letter of displeasure send him show cause notice and/or warning letter for code of misconduct

Dear Pinky,
Using foul language in official communication is also misconduct. Therefore, on the strength of the evidence of this misconduct, you may conduct one more enquiry. I recommend you not letting off employee with just warning letter as employee appears to be audacious. Though disciplinary enquiry against him in progress, yet if he foul mouths HR, it shows his arrogance. If such employee is shown the door the better otherwise he could create more headache to you in future.
Thanks,
Dinesh Divekar