“Snail mail” might not exactly be the communications wave of the future, but the United States Postal Service is trying to keep up with one emerging technology trend: smart phones.

A two-month promotion offers a 3 percent discount to businesses that include quick response codes on mailing envelopes. The stamp-sized bar codes can be scanned using a smart phone app, and users are then directed to websites.

The codes are showing up on monthly bills sent out by Westar Energy. Spokesman Nick Bundy said the codes help provide information about saving energy or promote various company products. Westar had already starting tinkering with the codes, Bundy said, and the USPS discount program “was really good timing.” Customers scanning the recent codes on their bills are directed to a website with energy conservation tips.

Judy Raney, Lawrence postmaster, said she hasn’t seen other local companies besides Westar taking advantage of the discount program, which runs through August. But Raney expects the codes to start popping up more often in the mail.

The codes are a way for the USPS to keep up with the changing technological landscape, she said.

“We’ve got to keep up with the times,” Raney said.