Dear XXXX,
This is to inform you that I am resigning from my position as [Job Title] with [Company Name]. My last day of employment will be [Date].
After much consideration, I have decided to move on to a new challenge elsewhere. I assure you that I will remain dedicated to my role and responsibilities until I leave and will do as much as I can to ensure a smooth handover.
I am most grateful for the support and opportunities that I have been given at [Company Name], and wish you and the company all the very best in the future.
Best regards,
XXXX