Rename attachments on the fly

 Renattach is a small, efficient and surprisingly effective filter
 designed primarily to offer an additional level of safety to Windows
 users whose e-mails pass through a UNIX-like mail server. Many modern
 viruses are spread through e-mail, and renattach combats such viruses by
 filtering e-mail attachments based on file extension. The idea is to
 rename potentially dangerous attachments (executable ones) so that
 the user, or the user's poorly written e-mail software, does not
 accidentally execute the attachment.