Sending a resignation letter by email is a way to let your employer know in advance that they should be expecting your formal . It is an act of courtesy and a polite way to make sure you leave your job on good terms.
Email Resignation Letter - Sample Letters
In this instance, your resignation letter email subject line should be concise and to the point, to ensure it is read immediately. Polite sample subject lines include: "Resignation: Name", "Notice of Resignation: Name", and "Resignation Announcement: Name."
job change - How does one title a resignation email
How To Write A Resignation Letter - Forbes