A friend asked me the other day if, in the past five years, I had ever been asked for my Twitter handle when buying a product. I laughed at the idea.

It wasn’t the concept of asking your customers if they were on Twitter that I found so bizarre. In fact, it makes so much sense; I don’t know why you wouldn’t do it.

What I found so funny was that he was suggesting that businesses should ask for something so (relatively) modern when so many have been ignoring the opportunity represented by email for years.

Remember, email marketing—more than any other form of marketing—remains the most cost-effective method of driving repeat orders to your business.

I can honestly count on one hand the number of independent, brick-and-mortar retailers who have asked me for my email address while I made a purchase in the past decade.

Why these businesses seem so happy for me to walk away from their stores without identifying myself as a potential repeat customer is a mystery to me. It would never happen in the online environment.

Do online retailers value their customers more than traditional businesses?

Of course not, and let’s be honest, many online businesses still haven’t grasped the opportunity of regular and properly targeted email marketing campaigns.

If you are not asking your customers for their email addresses when they enter your stores, you are missing a huge opportunity. Worse still, if you are asking your customers for their email addresses and not doing anything with them, what are you thinking about?

Perhaps you (or your staff) might feel awkward about asking for an email address, but really what is the worst that can happen? I would personally feel more awkward about turning future sales away.

Try and incentivize your employees to collect email addresses with competitions and small bonuses. You should also incentivize your customers with the promise of great future deals and relevant content.

Get email right first and then—who knows?—you might make that bold step to engaging (note: the word is “engaging,” not “broadcasting”) with them via social media.

How do you build your lists in the real-world environment? Share your success stories below.

This post first appeared on the iContact Email Marketing Blog.