As of early August, 145 million people in the U.S. owned smartphones, according to a comScore report from August 2013. Add to that the fact that email was the top activity of U.S. adults on their smartphones – based on a new study – and you’ve got an opportunity to reach customers anytime, anywhere. Some businesses are using this to their advantage, crafting emails that ignite action. Others, however, are provoking customers to take only one action: Clicking “delete.” Here are four common mistakes that turn marketing into junk mail.

No. 4: Making a tpyo in a subject line. If you wrote the email copy, get a colleague to proof it. Then send out a test blast to a different team member internally. We all make mistakes, but we can also all take the steps necessary to minimize them.

No. 3:  Writing an email subject line that’s so lengthy, it gets cut o… When your email subject lines are too long, they get truncated in the preview, which can be a total disconnect for your reader. While every email program is different, aim for less than 60 characters, including spaces, to ensure that your email subject displays properly in your recipients’ inboxes.

No. 2: Sending your email creative as a high-resolution image. Although photos are a great way to illustrate your message, if your entire email is one large image, you could run the risk of it not loading properly. That means your customers will see a red “X” where your beautifully designed email creative once appeared.

No. 1:  Burying the call-to-action. If you want the reader to take action after reading your email, you have to tell them what you want them to do. And telling them mid-way through the third paragraph of a long-winded eblast won’t cut it. Keep your message short and concise, with a clear directive at the end. In addition, use design elements, like a “Register Now” or “Subscribe” button, to help guide users toward the appropriate action.

What’s the worst email snafu you’ve ever made? Share it with us on Facebook.