In my opinion, subject lines make one of the most important parts of sales development. Even a highly-personalized and relevant email may never get opened just because of a weak subject line. The recipient will simply skip it.
For that reason, I’ve already covered some aspects of subject lines in my previous posts:
Subject Line Formulas for Email Outreach > read here
The Perfect Subject Line for Cold Emails > read here
Today, I want to share another take on this topic. But this time, I’ll back up my insights with some data to help you increase your average cold email open rate.
To get this info, we teamed up with Reply.io data science team a few months ago and analyzed millions of emails sent through our platform.
So let’s decode our key findings 🙂
1. Open Rate and Subject Line Length
I’ve always been curious: Could the length of your subject line influence the open rates?
Now, I have my answer: Yes! An average open rate correlates with subject line length. As you can see:
empty subject lines generate almost 60% fewer opens compared to an average result
empty subject lines generate 45.6% fewer opens in comparison to subject lines with only 1 word
subject lines with 1, 2, 3, and 4 words get the highest possible open rate, the fewer words - the better
Remarkably, an average reply rate declines if the subject line has 5 or more words, but an average open rate is the same whether you use 5 words or 11+ words in the subject line.
2. Open Rate by Letter Case
As an SDR leader, I often receive emails from other salespeople. So eventually I started noticing that many of them use all lower case words, e.g.:
And it got me thinking: does the letter case in your subject line really influence the open rate?
Well, according to our data, it can indeed influence the open rate, yet correlation isn’t that significant.
We’ve analyzed 3 variants of the same subject line:
all lower -> sales development process at reply.io
most lower -> Sales development process at Reply.io
most upper -> Sales Development process at Reply.io
And here’s what we’ve found out:
the average open rate for all emails was 31,69%
if the subject line contains most lower case words, the open rate would be 31,76%
if the subject line contains most upper case words, the open rate would be 34,15% (which gives us 2,46% more opens compared to the average result)
surprisingly, a subject line that contains all lower case words may generate 3.46% fewer opens compared to the average result. It’s also worth mentioning that the average reply rate here would be lower as well.
3. Open Rate by Number of Words
The next assumption I was eager to test was: could more variables like {{FirstName}} or {{Company}} help me generate a higher open rate?
So, we analyzed subject lines with 0, 1, 2, and 3 variables to see how this may influence our average open rate 👇
The subject lines containing 2 and 3 variables generate more opens (32.97% and 35.54% accordingly, while an average open rate is 31,69%)
Surprisingly, the subject lines with 0 or 1 variable get almost the same results.
This means it’s OK to send cold emails with no personalized variables in the subject line as long as the messages are relevant and timely. For example, if you’re reaching out to the prospects currently hiring salespeople, you can use a simple subject line like “Noticed you are hiring new SDRs” line without any variables and still have those prospects open your email because it’s relevant and personalized.
4. Other Stats
I also asked our data scientists to analyze a few more metrics to see if they have any impact on the open rates:
special symbols like &, !, ?, :, etc.
phrases like “follow up”, “quick question”, “referral”, “open for a chat”, “let's talk”, “partnership”, etc.
emojis 😉
Here are the results:
As you can see, trigger phrases help increase an average reply rate, while symbols tend to decrease open rates. Sounds legit, since I’ve seen other sources state that symbols like ? and ! lead to lower open and reply rates with cold outreach.
It also seems that emojis increase both open and reply rates. I haven’t been using this tactic in my outreach yet, but I will definitely give it a try and share the results later. So stay tuned 😉
That’s pretty much it. So, if you’re looking to up your sales development game, subject lines may be a good starting point.
Here is a checklist I’ve prepared for my SDR team based on the data-backed insights from this post. Feel free to steal it 🙂
Disclaimer: this research aggregated data on millions of emails sent via Reply, so it contains emails to prospects from different industries, countries, job titles, etc. So, if you already have better results with your campaigns, there’s no need to change anything in your outreach strategy (unless you want to experiment or A/B-test different options).
See you next time 👋