How about ' please be informed that XXX is no longer with ABC company. For future meeting invitations please send to YYY (ur boss) and copy me (email ). Thankyou.
呢d email我一般唔會用 resign 而用d中性d既term. (no longer with the company)
唔會用某人 resign 咗 咁核突。通常會話 某人 no longer with our company.
Regret to inform that xxx has no longer with our company. please kindly c.c. the mail / schedule to my attention effectively/ from now on as I will organize the schedule for Mr. xxx. Thanks for you kind attention and cooperation!