July 26, 2010 -- Email marketing open rates "continued a steady decline around the world," according to MailerMailer's Email Marketing Metrics Report, dropping from 12% in the first half of 2009 to 11.2% in the second half,"  as reported by eMarketer.

The MailerMailer report notes several possible factors contributing to lower open rates:  cluttered consumer inboxes, the increasing use of mobile devices, and the option of turning off of email images, which may deter an email from being opened.

Looking at email open rates by industry agriculture, religion, transportation and large businesses had the highest open rates, while entertainment, banking, marketing and medicine had the lowest email open rates.

The report found that "click rates suffered a much worse descent in the second half of 2009, dropping more than 38% from the first half and nearly 43% from the same period of the previous year" says eMarketer.

MailerMailer states that again inbox clutter was a problem, but also noted that "anti-phishing security measures sometimes stop links from going live. Email recipients must then take two actions—one to enable the links, and a second one to click on them."

The industry breakdown was similar to the one for open rates -- religion, transportation, environmental and retail emails saw the most clicked through. Legal, marketing, entertainment and restaurant industry emails had the lowest click rates.

According to MailerMailer, "the vast majority of actions will take place in the first 72 hours after sending a message, including about 90% of opens."