Re: Is email acceptable for resignation?
IMHO, it would be acceptable. The point came to where I was honestly burned out at a job a few years ago, and this was before email was as widely used as it is now. I sent a very tactful email and in my case, something along the lines of "due to a change in my circumstances, I am unable to continue employment . . . when would an appropriate time be for me to turn in my ID badge and/or conclude with an exit interview?" Perhaps something to that effect for you but pertaining to your situation. The willingness to come in for an exit interview and share whatever creative excuse you need to in order to keep the separation from your employer on a positive note.
As an above poster mentioned, it is a paperless world.
Of note, the particular job I had left via email and exit interview a week later - when they were in desperate need of employees two months later, they called asking if I was interested in coming back (uhm, no)