MailerMailer examined data from over 350 million emails in 21 different industries from the first six months of 2008. Here are some of the highlights of their report:

• How Soon Do People Open Their Email? – Much sooner than before! Nearly one third, 32.26% to be exact, of all opens occur within the first two hours compared to 29.57% six months ago and 29.40% a year ago.

• Open Rates – There was only a marginal decline in the average open rate, now at 13.20%, compared to 13.98% in the second half of 2007, which was a refreshing surprise after seeing these numbers tank last year. Recipients are opening emails just a little sooner, too. About 75% of all opens occur within the first 24 hours compared to 74% last year.

• Click Rates – Recipients continue to click at about the same rate they did six months prior, with click rates sliding down just by a hairline of 0.17% to 2.73%.

• Best Days to Send – Sundays, yes Sundays, and Mondays still hold the crown. Seems that a lot of us check email on Sunday nights to prepare for the upcoming week.

• Subject Lines – Our newest chart shows a pretty convincing metric: in general, the shorter the better. But you really should test what works best with your audience and the types of messages you send.

• Personalization – Personalized messages result in higher click rates, but now get lower  open rates, probably because so many spammers use this as a trick to get people to open messages that we are now conditioned not to open personalized emails.

• Deliverability – Bounce rates dropped again this half, meaning that more messages are getting delivered.

• Number of Recipients – Emails sent to fewer people were opened and clicked on more, just like in previous years. A smaller list size does not directly affect open and click results. However, mailings to smaller lists may be targeted better, contain more relevant content, or have more recent subscribers.

The full report will can be downloaded at http://www.mailermailer.com/metrics/