Dear [Recipient Name],
This is to inform you that I have accepted a position with [new company name].
I want to express my gratitude for a rewarding professional association during my employment with [current company name].
This decision was not an easy one and involved many hours of thoughtful consideration, particularly with respect to my own plans for my future. I am confident, however, that this new position represents a positive move toward fulfilling my career goals.
I hope you will respect my position in this matter.
My main thoughts now are to work as hard as possible to wrap up my projects here and turn over my responsibilities as smoothly as possible. However, I would like to join [new company name] as soon as possible. Therefore, if convenient, I would like to request that you waive my termination notice.