R.R. Donnelley, the nation’s largest commercial printer, has agreed to pay $22 million to the U.S. Postal Service to settle civil mail fraud charges that it underpaid postage on thousands of catalogs and other materials over the last decade. The Chicago-based firm allegedly violated an honor system that gives volume mailers a discount for presorting their mailings. According to the USPS, postal inspectors saw Donnelley workers inserting unsorted catalogs and magazines into bundles of mail that already had been processed for distribution, in violation of USPS rules. The company will work with the postal service to “develop certain solutions for Donnelley in those areas that are not in compliance with postal regulations” while helping to establish “realistic rules, standards and approaches that can be effected for the entire [printing/mailing] industry,” said Donnelley spokesman William Lowe.