Dear Sir,
This email to inform you that I am resigning from my position here as {job title}.
Attached in this email is my resignation letter.
Thank you for all of the opportunities this company has provided me. Please let me know if I can do anything to help make this transition smooth.
Again, it has been a pleasure working here and I want to wish everyone at {company name} the best of luck for the future.
Thank you.
Regards,
{Your name}