Why would you want to? Seems like an odd thing to do.
If I needed to go to a .csv, I'd do this: save the email to a text file,
open Excel, open (import) the text file into Excel doing all desired parsing
to get it into the columns you want, then save it to a .csv file.
If the body of the email is already in .csv format (that is, if someone took
a .csv file and pasted it into an email message), you could just save it to
a text file, open it in a text editor, remove the extra stuff, save it, and
rename it.
Andy