Smart companies purge duplicate names and addresses from their mailing lists, but duplicates can slip through even the most sophisticated systems. J. Jill, a Meredith, N.H., mail-order company that sells natural-fiber clothing for women, tries to save customers the inconvenience of having to deal with such unwanted mail. "Our catalog is printed on recycled paper, but an unwanted catalog is still a waste of resources, recycled or not," notes Liesel Walsh, manager of database marketing. J. Jill offers a $5 credit coupon to customers who alert the company to a duplicate mailing.

Why bother? "By using the precise mailing-label information from duplicate catalogs, we can improve the computer logic used to clean our mailing lists," says Walsh. Printing and mailing costs add up quickly. Eliminating just one duplicate mailing saves about $20 a year. Customers appreciate it too: Some are concerned about the environment, and some simply find it a nuisance to deal with piles of heavy catalogs. By alerting the company to duplicates, everyone makes a positive step toward a cleaner environment.