We have been asked more and more to create HTML emails, they look attractive and do allow for more visual exposure for the sender. The problem is security, email clients (most) by default do not display images unless they are attached to the email. This becomes a problem when sending out ~40,000 emails and its not viable to attach all the images.

Last week we sent out one of these emails, it was purely information regarding litter and cigarette butts on campus. Since there was no immediate action from the user it was difficult for us to track how effective the email was. So instead we measured how many users actually opened the email and viewed the images.

The reason for gathering these stats was mainly to advocate or deter from using HTML emails in the future. Most students on campus read their campus mail using the online interface which has a scary warning about viewing HTML images and we wanted to know how many students would get past the warning. Students also have the option to forward their email to another address, we were also interested to see where most students were forwarding their mail for better HTML email support.

What we did was setup mod_rewrite and a PHP script to upon loading a URL record the filename, timestamp, referrer and user agent. Then return back the image requested.

.htaccess

RewriteEngine On RewriteRule ^([a-zA-Z0-9]+).gif$ /email/index.php?image=$1.gif [L]

Example URL of image:

http://wayne.edu/email/header.gif

We then would pull out the records from the database and created the same log format as a web server, run it through a web log statistics program to get the results. This is what we came up with.

Total Sent: ~45,000 users Total Viewed Images: ~8,300

Visitors by Day:

Hours of the Day:

Referring Sites:

Conclusion: Most people who received the email did not open the image, only 18% viewed the images. Of those 18% only 45% opened the email in the webmail interface or in a desktop email client. The top three most popular forwarding addresses are Gmail, AOL and Comcast. And the most popular reading time is between 9-11 am and 9-10 pm. Although these statistics are only from 18% of the emails recipients, it goes to show nothing beats plain old text when you need to get important information across via email. Images should only be used for fluff and should not contain any necessary information.