Write a letter tendering resignation from current post.

This is to inform you that I have been presented with an opportunity that will enable me to work in the area of my stated preference, marketing. Therefore, I am tendering my resignation from your esteemed (name of company) and wish to inform you that (Date) will be my last day of employment.

I would like to thank you for the experience of having worked for your company, which is an outstanding organization. I wish you best of luck for your continued success.

Sincerely,