Charity smile train sent hundreds of thousands of letters with a once undone message, and it contained a reply card where each donor could check one of the three boxes. Households that got this once undone letter were twice as likely to become first time donors as people who got a regular, standard solicitation letter. Only a third of them opted out of future mailing. Most donors were very happy to let smile train keep harassing them. And over all, this once undone operation raised donations by forty six per cent.