Yesterday Business Insider reported on Groupon and its seemingly declining returns in their second oldest market, Boston. According to the post, while Groupon has added 21% more subscribers and almost 50% more featured merchants, Groupons sold per subscriber declined by 17.6% in the most recent quarter.

The equation for success in email marketing just isn’t as simple as more plus more.

If I’m the marketer, and I don’t have what you want when you want it, you won’t open the door for me. If my offer isn’t relevant, well-timed and of value to you, an increase in deals or frequency of offers isn’t going to get you to click – the relevance of the offer is the key ingredient to success in email marketing.

The offer and the timing are two primary components which create relevancy and result in engagement and stronger relationships with your subscribers. It doesn’t matter how many coupons you send out for bikini waxing. What matters most is who you send them to and when you send them. If you send 50 waxing coupons to swimsuit models at the start of the summer, you’ll have better results than if you send 5000 of the same coupons to the NFL player’s association list after Labor Day.

If the content doesn’t fit, then you can’t force it with increased frequency or more deals – that is not a sustainable strategy. Knowing each of your subscribers and their preferences based on their actual behavior will yield results.

As the email inbox continues to evolve, knowing your subscribers and providing relevant content to them will become more and more important. Those who get to know their subscribers will build strong profitable relationships and those who don’t will see diminishing returns as their list fatigue grows.

You can’t build a relationship if you don’t know anything about the person you want one with — what you say and when you say it can be the difference between a long term rewarding relationship and an unsubscribe request. That’s why Marigold Engage by Sailthru uses advanced behavioral analytics to help you know your subscribers so you can deliver relevant and engaging content when and how your subscribers want it, which reduces list fatigue and increases ROI on your email marketing.