It seems that this utopia is far from coming a reality though, as our Email Marketing Census shows that a large number of companies do not have any strategy in place for optimising email for mobile devices, with 32% reporting this as ‘non-existent’, and 39% saying their strategy was ‘basic’.

For companies in the process of working out how to optimise their emails for mobile, I thought it would be useful to round up a few case studies looking at how responsive design impacts user engagement.

So without further ado, here are the case studies plus a bonus infographic…

CareerBuilder increased CTR by 20%

After implementing responsive email design through ExactTarget’s platform, CareerBuilder achieved a 15%-17% increase in open rates and a 21%-24% increase in CTR.

It’s difficult to think of any reason why the open rate would increase due to responsive design, so this could be due to subject line optimisation.

Weird Fish achieved 10% increase in CTR

It’s a case study that’s slim on details, but Weird Fish increased the CTR to its website by adopting responsive email templates.



When DEG Digital created responsive emails for shoe retailer Crocs it began with a testing plan to learn and optimise the results of the redesign.

In the first test it created a three-way creative divided:

  • Group A received a static desktop version.
  • Group B received a static mobile version.
  • Group C received a responsive email design.

In this test clicks and opens were largely consistent for all three versions, but were slightly higher for the responsive design.

  • Total revenue and revenue per email were highest for responsive, followed by desktop, and then mobile.
  • Responsive and desktop achieved the highest AOV.

In the second test Crocs used an email that was less discount-focused and modified the way it tracked links to achieve more accurate results.

The test was a 50/50 split with one half receiving a desktop email and the other half a responsive email.

The results:

  • Responsive showed an overall 7.66% lift in click-to-open rate.
  • iPhone ‘read’ engagement had a 15.63% lift for the responsive version over the desktop version. Crocs is seeing more than 25% of all opens occurring on iPhone which makes optimising for this device even more important.
  • Mobile ‘read’ engagement had an 8.82% lift for the responsive version over desktop version.
  • Revenue on the mobile site was consistent for both versions.
  • Revenue on the desktop site was lower for the responsive version (since this test Crocs has launched a new responsive design website).


Footwear manufacturer Deckers, which owns several brands, moved to responsive email design when it realised that between 35% and 65% of its subscribers were opening their email on mobile devices.

But before committing to responsive design it ran an A/B test with its Tsubo brand, which had about 37% of its subscribers opening email on mobile devices.

The results of these A/B tests definitely leaned in favour of using responsive design. The emails that used media queries saw a:

  • 10% increase in click-through rates
  • 9% increase in mobile opens (iPhone opens went from 15% to 18%).

Deckers now uses responsive design for several of its brands. 

Userlicious also achieved 10% increase in CTR

Userlicious redesigned one of its client’s emails using a responsive template, coming up with this basic design: 

The intention was to design its emails for fat fingers and a small screen, including a limited amount of copy and shadows around the edges of the images to make them look like clickable buttons. The result was a 10% increase in CTR.

Scalable vs. responsive email design infographic