Introduction
Open Rate equals Number of Emails Opened (Unique) divided by Number of Emails Delivered, thus the answer is simple right? Just remove all inactive email addresses from your next deployment and I guarantee that your open rate will go up by over 25-50%! I'm assuming that's not where the marketer was going with their question. I wish for once that email marketers would ask me how they can provide an exceptional online experience to better engage their consumers through the email channel to meet their business objectives.
For years, Email Service Providers (ESP) told clients that the two key factors in a consumers decision to open an email were 1) the "from" address and 2) the subject line. These basic factors still hold true for a single email deployment but to look at your email communications longitudinally, the overall consumer experience has much more impact to the long-term engagement of a consumer with your email program.
Analysis

Consumer Experience: Email Marketing vs. Magazine Publication
Email Subject Line > Magazine Cover Call-out
Email Content > Magazine Table of Contents (Teaser Content)
Website Content > Magazine Article
So what does this mean for your email program? You can do all the subject line testing you want but if you do not follow through on relevant email content and web experience to fulfil your brands promise, you can expect a decline in engagement with your email communications further down the email relationship lifecycle.
Fulfill your brand's promise!
1) Does the "from address" reflect the brand communication the consumer signed up for?
2) Is the subject line relevant and does it align with the email and website content?
3) Does the email content fulfil the "promise" of the subject line?
4) Does the website content deliver on the value proposition that your subject line and email content "promised"?
Conclusion
Don't get me wrong, factors such as the subject line are critical to generating response activity (I will write a separate brief on subject line testing methodology in the future) but to generate long term relationships, email marketers must provide an exceptional consumer experience beyond the subject line. These closed-loop digital experiences will in turn result in... wait for it... increased Open Rates!
Colin Bhowmik, Digital Marketing Consultant, Open Rate
colinbhowmik@openrate.ca
http://www.openrate.ca/