About 2 years ago I received a quote in my yahoo email that on the bottom said "this email will vanish from your mailbox within 48 hours". And sure it did! I wo

About 2 years ago I received a quote in my yahoo email that on the bottom said "this email will vanish from your mailbox within 48 hours". And sure it did! I wonder how the author did that. He wasn't working for yahoo or anything like that; it was a quote not related to technology in any way. I'm still puzzled by this one. Anyone?