Improve E-Mail Performance With Testing, Part 1

One of the easiest, least expensive, and most overlooked ways to make e-mail efforts more effective is testing. This is true no matter what type of e-mail you send, no matter what your e-mail business goals. Through testing I’ve help clients realize:

  • A 7 percent increase in opens by mailing a few hours earlier
  • A 50 percent increase in clicks by adding a single paragraph
  • A 75 percent increase in sales by moving the offer copy

With e-mail, small changes can make a big difference in results. But organizations looking to test and optimize e-mail face two challenges: figuring out what to test and maintaining an apples-to-apples test environment.

Testing Approaches

There are two different ways to approach testing, both valid. Which you use is determined by your circumstance and the results you’re looking for.

If you want to get a read on how a single element will affect performance, change only that element for each test. If you want to improve performance and don’t need to link the increase back to a single element, test multiple elements all at once.

Let’s say your e-mail does very well overall; it meets or exceeds goals and industry benchmarks. You’re just looking to get a little lift in your open rate. That’s the time to test a single element.

But say your e-mail isn’t doing so well. You’re not meeting goals and are lagging way behind industry benchmarks. You may even be losing money every time you send. Then it’s time for a major overhaul. Test a number of elements, all at once, to really pump up performance.

What to Test?

Once you’ve figured out whether you’re testing a single element or a bunch, it’s time to identify exactly what to change. You can test just about anything, the key is figuring out which tests will boost performance the most.

One of the easiest ways to get a boost is to test sending e-mail on different days and at different times. When I tested sending a client’s e-mail newsletter at 12:30 p.m. versus 3:00 p.m., we saw a 7 percent increase in opens and a 10 percent increase in clicks from the earlier time slot. But don’t just shift your sends to Mondays at 12:30 p.m. — test it for yourself!

Proper test procedure is critical, particularly when you’re doing day and time testing. Here are some tips:

  • Randomly split your list into two or more groups. Use one as your “control” or “business as usual” group; make the other ones test cells with the elements you’re testing changed.
  • If you’re testing day and time, you obviously can’t send the e-mail all at once, but do send the groups as close together as you can to minimize outside factors:
    • When we tested sending at 12:30 p.m. versus sending at 3:00 p.m., we sent both e-mail messages on the same day.
    • If you’re testing Tuesday versus Thursday, send the messages the same week so there’s one day in between, not four.
  • When you’re doing a day or time test, keep everything else the same to avoid having too many moving parts. If you figure out which days and times are best, you can focus on testing your product, offer, and creative elements.

I like to break the other tested elements into categories, based on which metric is most likely to move. If you’re testing a single element, the key metric should have a domino effect on the actions that follow. A lift in open rates should translate into more clicks and more conversions. If you’re testing multiple elements, this doesn’t always hold. A lift in opens from one element may be offset by a decrease in clicks from another.

Elements Key Metric
Sender and subject lines Open rate
Anything in e-mail body (product, offer, creative) Click-to-open rate
Anything on landing page (product, offer, creative) Click-to-conversion rate

Next, I’ll cover some tips for testing sender and subject lines, e-mail body content, and landing pages. In the meantime, figure out what you want to improve about your e-mail and which elements you should focus on to reach your goals.

Until next time,


Jeanne is off this week. Today’s column ran earlier on ClickZ. Be sure to check out part two.

Want more e-mail marketing information? ClickZ E-Mail Reference is an archive of all our e-mail columns, organized by topic.

Related reading