Why do you insist on using a P.S. in an e-mail? (idea)

Another possible reason for writing a postscript in an e-mail is if, for some reason, you're using the old Unix mail program, or telnetting directly to the SMTP port (not much difference there) to send your e-mail. In this case editing previously-entered text is limited to erasing and retyping text on the current line of input.