How to develop a subject line testing strategy

Developing a strategy for email subject line testing

Hands up who has a strategy for testing your email campaign subject lines? Yeah you? Nice, well done. High Five.

If you don’t, then don’t worry, you’re not alone

As email marketers we know just how important the subject is to the overall success of our email campaigns. It’s the element of the campaign that drives open rates. 

So with that being said, it’s fundamental that we have a good strategy in place to test each and every campaign we send.

Because it doesn’t matter how compelling our off is, if no one sees it our hard work is for nothing

Benchmark and define your testing strategy

Before you start testing, it’s important to know where you are with your current open rates. 

You need to benchmark against you own results. While it’s tempting to look at industry benchmark reporting you should take these only as a rough guide.

Your audience will be different to that of those included in any benchmark reports so don’t place too much emphasis on these

After determining where you stand you need to decide where you want to be. The idea here is to be specific. I want to increase open rates by X%. Make this number achievable. Even small increases in open rate can lead to high increase in the actual number of people opening your emails  

Once you decide where you want to be, you need to decide how you are going to get there.

Here you need to decide what you are going to test and why.

It’s not good enough just to think of two subject lines that are a little bit different, that’s too vague and again not specific enough.

Here’s an example:

You might want to test a personalised subject line vs non personalised. Or you could test having a call to action in the subject line vs a more standard formal type.

Then you might want  to test an offer in the subject line vs no offer. Perhaps offering a percentage discount works better than a monetary value or vice versa

Whatever you decide you want to test, be consistent with it. You must test over a period of time and monitor the results. Depending on the size of your list and the frequency in which you send, this could take several weeks.

Not every test you run will yield a clear winner either. Sometimes you’ll see only a small increase between one subject and the next. Refine what your testing and try again.

Remember it’s OK to fail, if a subject line test bombs don’t worry about it. You’ll learn more about what works to your list from these campaigns.

Once you’ve tested and found what works then this becomes your control. Run this on a few campaigns and see if the results remain consistent.

Find something else to test against that. You can be continually refining your strategy and soon you’ll have a set of subject line formulas that work for your audience.

You can then use these to create your own benchmarks to measure your success against.

So in summary, to develop your own subject line strategy you need to

Know where you currently stand

Know where you want to get to

Decide what you are going to test consistently over a number of campaigns

Analyse the results and act upon them

Test again


Good luck – you got this!

Phil Monk

View posts by Phil Monk
Email Marketing Consultant with over 14 years experience within the email marketing industry.

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