Total email volume per sender is up almost 5 percent this year, according to Experian's Q4 2012 Quarterly Benchmark Study. But marketers should be wary of thinking that more is better, argues Strongmail's Justin Williams in a piece on ClickZ. He breaks down the numbers and illustrates how sending more volume can increase revenue on a mailing, but argues that over time it can increase unsubscribes. Instead, he says that marketers should focus more on A/B testing which can increase ROI without leading to list churn.