Earlier this summer, Brafton reported the findings of an ExactTarget survey that showed email marketing is key to boosting ecommerce – but nearly half of U.S. consumers would discontinue business with a company that didn't offer pertinent messages. Relevant content has always been critical to email marketing success, but the stakes may be higher now that major email providers are offering consumers new decluttering features.

One major email development marketers should know about is the Gmail Priority Inbox. The tool distinguishes different types of messages for users by deeming mail as "important and unread," "starred" (messages that may be looked at later) and "everything else" (mail that is less important or may be spam). The priority inbox works according to consumers' habits, with mail that is opened and responded to more likely to make it into the top slot. Of course, users can manually make changes if they are dissatisfied with the results.

Microsoft's Hotmail also launched new features that "eliminate all inbox clutter, not just the spam." The new Hotmail similarly accomplishes "individual preference auto-learning" based on user engagement to discern how specific consumers prioritize different types of messages. A Sweep menu is particularly good at decluttering, as it allows users to "sweep" their mail into folders to get them out of inboxes.

If marketers want to get their email messages into the inboxes of choice, relevancy will be more important than ever. It's time to assess email marketing campaigns and avoid any broadcast approaches.

Messages should be segmented according to customer behaviors, and targeted promotions should be provided to different clients. Good subject lines will also be key to boosting open rates; marketers should emphasize the email's offer upfront.

Creating relevant email content could really pay off for brands. According to a report from Epsilon, 12 percent of consumers say emails are the most trustworthy sources of information about products and services, making the platform the second most-trusted digital channel after company websites.