In this article, Stefan Pollard explains how to make your email campaigns mobile-friendly:
1. Reformat text
You should always offer a text option as an alternative to HTML for all readers. You can send this version to your mobile readers, but you might also have to reformat it to make it show up better on the smaller screen.
Most text messages have 60 to 80 characters per line. Mobile platforms will show 20 to 40 characters in 12 to 15 lines per screen, depending on screen width and type style.
Desktop-friendly line lengths can create long paragraphs in the mobile reader. If you use typographic devices as copy separators that also run 60 characters, for example, you'll give up four to five lines on the screen for something that adds no value.
2. Rethink tracking URLs
Same goes for URLs. Tracking URLs can also consume four to five lines per screen. If you can, use a simpler URL even if it means sacrificing some tracking ability. These long URLs can result from automatically reformatting HTML copy into text, so your text version may need some hand-tweaking in order to render better on all platforms.
3. Be brief.
Message size must come down whether you send in text or HTML. Messages over a certain size -- even as small as 12KB -- risk being cut off halfway through. In many clients, your reader can opt to click a button that will call up the rest of the message, but do you want to throw up that obstacle?
Personally, I hate it when I open a message and find "message truncated" right at the top. I need more to make me want to click the button that will deliver the rest of the message.
Another message I get that frustrates me to no end is "This message contains a rich-text HTML portion. Consult your mail client's documentation for information on how to view it." Uh, I don't think so. Delete! That means it won't be there when I get to my desk.
Also, rethink the content itself. Long sentences in long paragraphs force more and more scrolling. This also can be a barrier to conversion or another source of frustration for readers.
4. Validate your Web site, too.
Is your Web site mobile-friendly too? Probably not, if you haven't had it redesigned specifically for mobile applications. If you have to send readers to your Web site to get the most value from your email marketing, better make sure it will also render on their devices. You can check it easily by using a new validator developed by the World Wide Web Consortium: http://validator.w3.org/mobile/.