And?
Seems like a reasonable way of combating unsolicited e-mails containing zips which in turn contain .exe files that if run would cause damage. If the sender renames it and resends it you can be confident that the sender is known, and not malicious. My company doesn't allow .exe and a few others through, but does allow zips. However I have an idea that their mail filter program looks at the filetypes within the zips, which achieves the same thing.