The great thing about the POP mail protocol is that it is a well-documented open standard, making writing a mail client to collect mail from a POP box a relatively painless process. Armed with basic knowledge of POP, or SMTP it is possible to write proxies which do a variety of useful things, such filter out spam or junk mail, or provide an e-mail answering machine service. Unfortunately, in trying to write a standalone client for Hotmail, the world’s most popular web-based mailing system, the fact that no POP gateway exists rapidly becomes a problem.