Now that mobile devices have become ubiquitous – Imageand range from smartphones to iPads to eReaders to netbooks – the question is not “if” you need a mobile strategy for your email marketing program, but “when.” A recent study by Nielsen found that 40 percent of the US mobile users now own smartphones. And earlier research from the Pew Internet Project discovered that 87 percent of smartphone owners access the internet or email on their device, two-thirds of them every day.

You are only ready to go mobile when you can offer a complete mobile experience. Your mobile website needs to be live and engaging – otherwise, you are linking to a weak experience. If you don’t have a mobile website yet, focus on formatting and length for your mobile readership. Start with these three key questions to get your program ready.

How much of your audience uses mobile?

There’s no doubt that smartphone prevalence is enormous –and growing. But, before you invest in a mobile experience, you need to know what percentage of your audience reads your emails on a mobile device. They may spend the entire day on their devices, but that does not necessarily mean they interact with your messages. There are several pixel-based tracking services that can help you track activity, audience segmentation, types of devices and the response activity where devices are a differentiator. You might also consider offering a mobile option in your preference center to help you gauge how popular mobile is for your specific audience.

Do you have content particularly well-suited to mobile?

It makes perfect sense to generate mobile-specific messages for some content. For example, daily deal coupons or information targeted specifically to travelers may warrant mobile make-overs. However, many marketers start with a “middle-of-the-road” approach, at least initially. Even the most avid mobile users still access some emails on desktops, so it’s probably not optimal to design all messages only for mobile. Start slowly, test, measure and let those results guide you.

Remember too, that mobile email design can change some of the fundamentals. It’s more than just the brief copy, streamlined navigation and narrow table columns. We must design for fingers, not mice. Links and buttons must be easy to read and navigate. There is also no alt text or “hover” state for a touch screen.

Have you adapted your message to readers who are on-the-go?

When you’re ready to create email messages specifically for mobile, tighten your focus and make sure the content is short and succinct. Mobile users typically scan emails while they’re waiting to do something else, so their attention spans are particularly short. Don’t waste their time. As with any effective email marketing campaign, your goal is to target content so you’re delivering the right message to the right person at the right time. Use compelling (and short!) subject lines to engage the reader and focus on increasing the personal and external relevance of messages to make sure you’re connecting. In addition, it’s important to remember that smartphones are individualized digital eco-systems. Users are likely to be unforgiving if they think you are spamming this personal space.

Segmenting mobile email messages from your overall email campaign can be very beneficial, provided you identify where mobility is a differentiator and then adapt your content to the small screen. As always, your goal isn’t to “just sell.” It’s to engage and build a relationship. Use a consistent, integrated and thoughtful approach, and your mobile email campaign can lead to a considerable competitive advantage in today’s increasingly mobile marketplace.