My present personal circumstances no longer allow me time to work in your company. With this issue, I am emailing you this resignation letter which is effective today.
I want to apologize that I have to resign on such a short notice, knowing the amount of work that needs to be done in your company. Further, I ask for your forgiveness in not giving you a paper copy of this resignation letter. Pardon me, but this email is all I can do by now.
I know that other company departments still require a hard copy of an important document such as this. Let me assure you that, circumstances permitting, I will be giving you such letter.
I am quite honored by the work experience I have done for the company. The experience which I have garnered during my tenure will serve me well in the future.