Marketing e-mails are widely accepted as obnoxious, though they are the darling of the marketing team's online arsenal. But the infamous inbox clutter may finally be losing marketing steam. A November 2008 study by MailerMailer shows that fewer consumers worldwide are opening marketing e-mails. The average open rate fell to 13.2 percent in the first half of 2008, compared with 16.11 percent in the first half of 2007. Click rates also fell from 3.18 percent in the first half of 2007 to 2.73 percent in the first half of this year. Specific criteria affect open rates, including what business categories the e-mails originate from and the length of subject line. Some industries had higher open rates for their marketing e-mail, among them banking and finance, religious and spiritual, government and telecommunications. E-mails with subject lines of less than 35 characters yielded open rates of 19.6 percent and a 3.1 percent average click rate. When the subject lines exceeded 35 characters, the average open rates dipped to 14.8 percent and a 1.9 percent click rate.

Even if the efficacy of e-mail marketing may be waning, it is not likely to end any time soon. In July and August 2008, 241 online retailers reported marketing distribution to E-Consultancy and R.O.EYE. Of online marketing channels that retailers utilize worldwide, only paid search yields a larger percentage of high volume sales at 44 percent. E-mail marketing drives 32 percent of high volume sales, ahead of affiliate marketing (fifteen percent), online display advertising (ten percent) and mobile marketing (three percent). While the sample size was relatively small, eMarketer found similar figures in other 2008 surveys by Radar Research. E-mail marketing yielded the best return on investment of any tactic.

The dip in opens and clicks are a premonition of an online marketing shift that will take some time to manifest. In the meantime, best to leave the spam filter on.