Text message marketing is anything but fringe when it comes to driving business. In fact, Mshopper notes that successful SMS campaigns have huge potential, with engagement rates reaching eight times the level of typical email campaigns. A number of retailers, meanwhile, have managed conversion rates as high as 23 percent. Given the brevity and immediate delivery of SMS marketing, the campaign strategy can be very economical and useful to businesses looking to build their client base. But SMS campaigns also deliver marketing materials to a rather personal virtual space: The consumer’s text inbox. As a result, it’s important to respect this access while making the best use of your SMS…