The travel industry recorded the largest increase in email volume during the fourth quarter of 2012, according to Experian Marketing Services' 2012 Q4 email benchmark report. Two-thirds of travel brands increased mailings, which made email volume rise 21.4 percent year-over-year. The volume of emails sent by publishers was up 14.3 percent and consumer products and services brands saw volume go up 10.4 percent during the quarter. Overall, email volume was up 5.4 percent during the quarter.