There is a version of the 80/20 rule in email, where the majority of your clicks come from a minority of subscribers. Your email ROI doesn’t suffer as long as the 20% (or so) drive the registrations / subscriptions / revenue / etc. that you need. But there is a hidden cost to emails that cater only to a minority of subscribers, regardless of near-term ROI. If your emails do not appeal in some way to most of your list, engagement will wane and unsubscribes will increase.

The reason that many people do not respond to your emails may have nothing to do with a lack of engagement with your brand; rather, they may just not be in-market for whatever it is the email is selling. Spend a few months sending messages that do not speak to them at all and they may no longer be around when they are ready to purchase. Remember, your email program has to meet your organization’s needs today as well as next year.

Even if you don’t have Big Data to tell you who from your list is in-market and automatically serve them a customized targeted message, there are still ways to use email to keep customers engaged throughout the purchase cycle. Here are a few ways to make your promotional emails engaging for subscribers outside the buying cycle, without limiting their appeal to those who are in-market:

1. Fill the gaps between purchases with content marketing: Most companies are now producing some kind of content marketing, such as blogs, videos, white papers and photo galleries. Featuring links to some of this content within your promotional emails can help qualify customers close to making a purchase as well as give out-of-market subscribers something to click on within the email. For example, if you are promoting an upcoming conference, only the in-market prospects will pay a lot of attention to links to the agenda or registration pages. But prospective attendees and non-attendees alike may be interested in a photo gallery from the cocktail reception at last year’s event, or a video of a different presentation the scheduled keynote gave recently.

2. Solicit comments and testimonials: Some subscribers are not interested in buying what you are selling in an email because they bought it already. Maybe their subscription is current or they attended a conference last year and it is a colleague’s turn to go. You can keep them engaged by soliciting comments and testimonials. A surprising number of people are happy to share when asked (witness the popularity of Facebook brand pages and how many comments they generate). Try working into your emails requests for comments and point people to your Facebook, YouTube or Instagram pages, to a product review engine on your site, or a testimonial form you set up expressly for the purpose. You may generate more clicks to read the feedback than to contribute, but that is a victory in itself.

3. A/B test content organization: One of the decisions you’ll need to make is which content to feature in your messages – the principal call-to-action for your in-market customers (eg. “Register today” or “Buy now”) or some of the content that helps qualify in-market customers while also keeping the rest engaged until they are ready to purchase. Experiment with different layouts and try A/B testing to see which layout works the best. If your subscribers are engaged, you will see a lot of click activity even at the bottom of your messages. If they are not, bumping up the content most likely to aggregate clicks may work better. Do this frequently, as every new offer will have new sets of in-market and out-of-market subscribers.