You know the type: Quick to sign up for your company’s email list…and just as quick to unsubscribe. Here’s why you shouldn’t sweat fair-weather followers.

Email remains the most effective way to promote your product to customers, yet it’s also one of the least monitored. Do you know the markings of a “good” email newsletter?

According to a recent email marketing census performed by the digital marketing firm Econsultancy, less than 33 percent of marketers regularly check their email newsletters for efficiency. Of the companies that do perform regular checks, however, 74 percent found their email marketing ROI to be excellent or good.

So what are these companies checking for?

In email terms, a high return translates into one thing alone: The number of subscribers on your mailing list, writes marketing blogger Beth Hayden. Your list should be growing over time, she explains. That means consistently gaining more subscibers than you lose.

But what about the dreaded fair-weather subscriber: The consumer who signs up for an email newsletter, perhaps to benefit from a promotion, and promptly unsubscribes again as soon as he is able?

Don’t worry about that guy, Hayden writes. He’s actually doing you a favor. She writes.

“There are going to be people who drop you because you want to sell them things. These people want to get great content from you, but get angry or upset when you make offers for relevant products or services…You want these people off your list. As they self-select out, give a little cheer. That’s one less person on your list who wants you to work for free. And that’s a beautiful thing.”

Another reason to rejoice over cancelled subscriptions: It actually saves you money when fair-weather subscribers bail, writes Hayden.

“Most email service providers charge fees according to how many names you have on your list,” she explains. “As your list grows, it costs you more…If you’re going to be paying for each subscriber, you need each of those contacts to be to be as qualified as possible.”

Hayden concludes: “When people voluntarily unsubscribe, it actually saves you money. You’re no longer paying to send emails to people who aren’t interested in your content and will never buy your products and services.”