First impressions are crucial to the success of any business relationship, regardless of the medium. From our research on advisers, we’ve found that some are receiving a dozen emails from asset managers every day so it can be difficult to stand out among the crowd. So, since the subject line of your email is the first thing any potential client will see and the only thing between your potential client and your email, the content of the subject line of your email is as important as what’s inside it. The subject line’s only job is to get people to open the email, so it needs to catch the readers attention, pique their curiosity, and/or appeal directly to their needs.

But how can you be sure the subject line you landed on will work better than one of your alternatives? Well, why don’t you ask them? With A/B testing you go straight to the source and let a sample size of your audience decide which subject line they prefer.

In order to get the best results from your future testing, here are a few helpful tips on how to optimize your A/B tests:

Test as large a sample as you can for more accurate results

If you want to get an accurate read on your audience’s preferences, you need to send your test to a statistically significant sample size. The larger your audience, the smaller the audience percentage you need to test. As a general rule of thumb, if your email list is smaller than 1,000, you should test at least 50% of your audience. If it is larger than 1,000, ~30% will be sufficient.

Give people time to weigh in

When you set up your A/B tests, make sure you give plenty of time for the test to run so you can record a significant amount of responses. Financial advisers are always on the run so they may not be around to check their inbox whenever you send your campaign. If you give the test too small of a time frame than you risk a large portion of your test audience not even getting a chance to see the email before a winning subject line is decided. If the timeframe of your email isn’t urgent, give the test 3-4 hours to collect data.

Listen to your data, not your gut instinct

It can be hard to shut out that little voice in the back of your head telling you that you know what’s best when it comes to choosing a subject line but, even though you may be right a portion of the time, forgoing the conclusions of your data from previous A/B tests in favor of your gut feeling negates the whole purpose of testing in the first place. Once you set up the test, the data determines the outcome automatically, but when it comes to applying what you learned from previous tests, you have to trust what your audience has established in prior A/B tests. Trusting your data is the equivalent of trusting that your audience knows what they want.

Don’t rest on your laurels

Too many email marketers fall victim to what I like to call “The Wile E. Cayote Fallacy” when it comes to testing their subject lines. This all too common mistake occurs when one conducts an A/B test and, whatever the result, one regards it as infallible and never tries it again.

Just like the classic road-runner-chasing Looney Toons character, Wile E. Coyote, would try different Acme products to capture his illusive prey and, whenever they would inevitably fail, even if it was sheer coincidence and not the fault of Acme’s shoddy rocket-skate manufacturing, the coyote would always give up and move on to the next contraption Acme had to offer. The coyote never stopped to consider that maybe if he tried the 10 ft. tall slingshot a second time, now that he had a practice run and was comfortable with how it worked, he would possibly get a different result.

The point is you should test the same hypotheses more than once to ensure your initial result wasn’t just a fluke, otherwise your email marketing efforts run the risk of slamming head first into the brick wall with a tunnel painted on it that is marketing entropy.

Only test one variable at a time

Just like when conducting a science experiment, eliminating as many variables as possible is paramount to success with your A/B tests. You want to be absolutely sure it was your subject line that caused the change in engagement and not some other aspect of your email, otherwise your data becomes less reliable.

Brevity is the soul of clicks

The last thing you want to do is lose your recipients’ interest mid-subject line. If you’re conveying too much information right away instead of coaxing your readers into the email, you’re likely to have one of two things happen: 1. Your subject line will get cut off by whatever email client your recipient is using, or 2. Your recipient will get bored and immediately move on. Here is a quick guide detailing how many characters each type of email client allows:

Subject line length chart

Source: Campaign Monitor

Ask the right questions

Wording your subject line in the form of a question is a great way to rouse the interest of your recipient and stand out among the clutter of their inbox. Try A/B testing it against the same sentiment formatted as a statement and you will most likely see the question win out time and time again.

Know the difference between “excited” and “spammy”

It’s perfectly acceptable to be exuberant about the message your sending since if you weren’t, why would your recipients? The important distinction to keep in mind here is that when you display too much exuberance you quickly stop sounding like a real person sending a genuine email and start sounding like a fake African prince sending an email fishing scam. The point being, when it comes to capital letters, exclamation points and emojis, use a light touch.

Be specific

The clients and prospects receiving your emails want to know what they’re getting into before they click on one of your emails so make sure to be completely candid in your subject line. This isn’t to say intentionally curious or captivating subject lines aren’t encouraged, but more so that vague or possibly misleading subject lines should be avoided at all costs. Financial professionals are very busy and therefore it is key to keep things clear and concise as to not waste anyone’s time.

Have a plan

There is no sense in taking mad stabs in the dark regarding your subject line split testing since that will only get you so far. Establish exactly what you would like to know about your audience’s behavior and work backwards to develop your test(s) around that issue.


The only real way to find our more about the nuances of your audience’s preferences is to test them out and see what sticks. Test early. Test often. Test confidently with StoneShot.