We work in an increasingly mobile-oriented world. The Pew Research Center found that the use of phones to read email doubled between 2009 and 2013, and the November 2014 Ericsson Mobility Report estimates that smartphone subscriptions and traffic per phone will have respective annual growth rates of 15% and 25% until 2020. These trends raise many questions, especially for email marketers. Here are two we wanted to answer: “What will mobile’s impact be on email engagement? And can email campaign design counteract changing engagement rates?”

Methodology

We analyzed a random subset of email addresses that MailChimp sends to and determined their corresponding devices from their user agent strings. For each address in our sample, we considered the device that registered the most clicks to be that user's preferred device. To focus on recipients that actually engage with email, only addresses that had clicked on an email campaign since the beginning of 2013 were considered.

We aggregated sends and clicks to these addresses from MailChimp users within a 6 month period to see how preferred device impacts engagement. We looked to see if use of our Inbox Preview feature and responsive templates help engage mobile subscribers, and we looked at how different links within a campaign are impacted.

Readers click less on mobile

What did we find out? For starters, PCs, tablets, and mobile devices accounted for 64%, 9%, and 27% of email addresses, and 72%, 9%, and 18% of clicks, respectively. Right off the bat, we could tell that PC users click more.

Next, we calculated click rates at the address/campaign level. Unique click rates measure what percentage of sends received at least one click, and total click rates allow for multiple clicks for a single recipient/campaign. We found that PC and tablet users have unique click rates of 3.8%, a 40% increase over the 2.7% mobile click rate.

Unique click rates for PC and tablet users are similar, but PC users who click tend to click more links per email than tablet users, resulting in a 6.7% total click rate for PC users and a 5.6% rate for tablet users.

Recipients who use mobile phones had unique and total click rates of 2.7% and 3.9%, worse than all other device categories. Of the three platforms, PC users are more likely to click on an email, and those that do tend to click on a larger number of links within that email.

We now know that a huge chunk of users read email on mobile devices and that they have lower click rates, but does this impact all parts of a campaign? To answer this, we classified links by how far into a campaign they were and calculated click rates. We did this by determining whether a link was the first, second, third, etc. within a campaign. We then counted the total number of sends and clicks to each link depth for various types of campaigns and users. (We only considered links with a depth of 10 or less to focus on link depths that are more commonly found in email campaigns.)

Although campaigns have total click rates of 4%-6%, these clicks are not distributed evenly across all links in a campaign. In reality, any single link probably has a click rate of .25%-1.5%. PC and tablet users still have higher click rates, but deeper links get fewer clicks for all devices. The fifth link in a campaign typically gets half as many clicks as the first link.

Responsive design can improve engagement

There is some cause for concern here, but there’s also hope. First up: responsive email design, which adapts to different devices and screen sizes. Our research shows that MailChimp’s responsive email templates get higher click rates on all devices. They are particularly effective on mobile users, where the increase in unique clicks from 2.7% to 3.1% represents a 15% increase in actual clicks.

Campaigns that use responsive templates have higher click rates in general, but the impact seems to be mixed at the link-depth level. Only the first 3-5 links typically see a benefit from the use of a responsive template.

If you’re a MailChimp user, another tool at your service is Inbox Preview. This feature allows you to see what your campaign will look like on various devices before you hit send, giving you the opportunity to tweak your content or design if necessary. Responsive templates increase clicks by 5%-15%, but Inbox Preview increases clicks by 13%-24%. It works particularly well for mobile and tablet users.

Using Inbox Preview results in more evenly distributed clicks throughout a campaign. Click rates for links at the top decline slightly, but this is counteracted by much higher click rates on deeper links. Click rates for the tenth link in inspected campaigns were double those of non-tested campaigns and were comparable to rates for the fifth link in non-tested campaigns.

Taking a more conscious approach to designing your campaigns will help your content fit the screens and attention spans of mobile recipients. Will this all get thrown up into the air once Android Wear, Apple Watch, and Google Glass become the norm? It's too early to say, but for now, your best bet is to design emails that look good on devices of all sizes. It's always better to be ahead of the game than behind the times.