Consumers and lawmakers are rightfully wrathful about "spam texts." But a well thought-out, opt-in advertising campaign delivered by text to people's smartphones can be a highly effective marketing tool--a much better one than email.

"People sign up for email opt-in lists all the time, but 95 percent of email is spam, and with the typical user getting hundreds of emails a day, even if you've opted in, marketing email can get lost by the wayside," explains James Citron, CMO of payvia, a mobile messaging and payment service. The danger of marketing emails being ignored is especially high now that Gmail automatically divides inboxes into three or more folders, automatically gathering promotional emails into their own ghetto, far away from the "primary" messages users are likely to prefer.

On the other hand, Citron says, promotional text messages have a 95 to 97 percent open rate. Email open rates are currently hovering around 28 percent. That alone seems a good reason to give text marketing a serious look.

Here's how to do it right:

1. Make sure customers really do want your texts--and you can prove it.

Just to reiterate, sending unsolicited texts can get you into trouble with the FCC, mobile carriers, and your customers. So don't do it! That said, we all know that some people sign up for messages they don't really want via inattentiveness or forgetfulness. Since spam text is illegal, make sure you keep a permanent record of customers' opt-in agreements. Have them do something quite deliberate to begin getting your texts, such as texting a keyword or snapping a picture of a QR code with their phones. And every text (like every promotional email) should include simple instructions for opting out, such as replying with the word "stop."

2. Be tempting.

The 2008 Obama campaign enticed a legion of supporters to sign up for texts by promising to let them know first who the vice presidential candidate would be. You can draw in subscribers the same way by promising coupons, special sales or freebies, or other goodies. If you can provide information that users want on the go, such as local restaurant reviews or tips on local events, that can be another temptation.

For instance, payvia provides text marketing for a popular song-based TV series (hint: it starts with a "G"). "People who sign up for the texts get the songs before everyone else," says Tracy Kunzi, director of client strategy.

3. Ask what customers want. Then give it to them.

How often is too often to send marketing texts? Citron says there's a failsafe method for texting customers just the right amount: "Ask them when they would like to get messages and what info they want. And then customize your text marketing program to suit their preferences."

It goes without saying, he adds, that you should never use bait-and-switch tactics on customers. "Send what you promised to send, and don't stray from that."

4. Be considerate.

Be thoughtful about the moments you choose for sending text messages. Don't send texts after 9 p.m. or before 9 a.m.--and keep time zone differences in mind. Keep things like holidays in mind as well.

5. Think outside the alphabet.

It sounds like an oxymoron--visual text marketing? But, Citron points out, most phones in use, even fairly old ones, can receive MMS (Multimedia Messaging Service) texts, as well as the more familiar SMS (Short Message Service) texts that are limited to 160 alphanumeric characters.

You can use MMS to send images or short videos to your customers' smartphones. And while an SMS can, of course, include a URL for a YouTube video, "YouTube on a mobile device can reach 50 to 60 percent of Americans, while an MMS can reach nearly 100 percent," Citron claims.

What should your images or video show? "Express your brand," he advises, "And combine utility with something of value to the customer." That will keep consumers happy to open your texts.

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