Analysis
The length of a subject line
The length of a subject line impacts the open rate. The longer the subject line the lower the open rate. Our findings show that the ideal subject line is only 4 words long – this length subject line performed best, with open rates as high as 60.17%.
According to our research, subject lines which exceed 15 words perform significantly worse than the ones below 15 words – their open rate drops to 31.56%.
4 words are enough to make the subject line appealing but short enough to fully display in your prospect’s mailbox. No wonder that longer subject lines perform worse, as 40% of emails are read on mobile devices.
For more details, have a look at the graph below.

“Quick question” subject line – does it actually work?
Many influential (and less influential) sources often recommend using the “quick question” subject line. It might have worked in, like, 2006, but is it still effective today?
Turns out, no.
Emails sent utilizing the quick question subject line had an open rate of 38%. Which is 20.83% below average. It is absolutely time to archive “quick question” to the Great Junk Folder in the Sky.
The power of personalization
All outbound sales experts claim that personalized subject lines work better. We decided to evaluate this claim using hard data, and here is what we found.
Subject lines with any kind of personalization tend to perform better than non-personalized ones. They get a 50% open rate which represents a 4.17% improvement over average.
How can you make the most of personalization, i.e. which custom fields are the most effective?
Subject lines which include a company name perform best – at 56% which represents a 16.67% improvement over average.
Additionally, if we combine this lesson with the previous finding about subject length, we are starting to see a major lift in performance. For example, a less than 5-words subject line, incorporating a company name custom field, will generate a 60% open rate – 25% improvement over the average.

Subject lines indicating that “you would like some of their time”
Subject lines which include a keyword indicating you would like some of your prospect’s time like mins/minutes, time, meeting etc. tend to perform worse than those without. For example, emails which included “time” in the subject line had an open rate of 30% while those without had an open rate of 48%, which is 47.92% below average.
There is an exception to the rule, however. Subject lines which contain the word “demo” or “call” work better than those which do not include any of the two. “Call” subject lines perform significantly better than the remaining subject lines, with an OR of 63%. This represents a 31.25% improvement over average.
Check out the graph below for more details.

Using deceptive subject lines
How about tricking your prospect into opening your email, will this work? Even if it did… do you really want to be THAT person? Good news, you do not have to lose sleep at night because the answer is NO. No it does not.
Using deceptive subject lines like adding “re:” or “fwd:” to your initial message, or “urgent”, “action required” will not only have a negative impact on your OR but it will also seriously annoy your prospects.
They have been tricked many times before, and they have definitely learned their lesson, so just quit it.
Subject lines which included “attention”, “urgent”, “action required” had an OR of 23% and performed 52% below average. While subject lines which included “Re/fwd/fw” had an open rate of 44% which is 8.33% lower than average.
The graph below includes more details on this subject.

Using marketing practices in your outbound campaigns
Sometimes marketers forget that sales emails are very different from marketing emails, meaning their outbound emails look too much like newsletters — which hurt their OR’s.
Including words such as “free”, “help”, “quick”, or numbers (e.g. “Want to boost your sales by 30%?”) have a detrimental effect on ORs.
Asking a question in a subject line has an OR of 36% and performs 25% below average.
The table below clearly demonstrates that subject lines which do not include any “marketing related” keywords perform significantly better than those which do.

Message preview matters
Your message preview (i.e. the part of the email your prospect views before opening it) impacts your open rate. Are you surprised? Well, do not be. We all get hundreds of emails a day and are actively looking to suss out irrelevant emails quickly, without missing relevant ones. Your prospects are adept at quickly scanning a preview line and deciding if it is worth their time.

We have decided to analyze the first 70 characters displayed in the email’s body, and here is what we found.
Starting your email with generic statements usually has a negative impact on your open rate. These statements include:
- Being apologetic (“sorry/apologies/pardon/excuse”) – which has an open rate of 34% which is 29.17% below average.
- Being polite (“hope you’re well/everything is well”)- which has an open rate of 38% which is 20.83% below average.
- Introducing yourself (“My name is/I am/I’m”)- has no positive or negative impact on your open rate which stands at 49%, but represents a wasted opportunity as it does not add any value to your prospect
- A pleasure to meet you – this is an interesting one, as it has got a whopping open rate of 87% which is 81.25% above average. It is a risky approach, however, as you are indicating to your prospect that you got introduced to them. Being deceptive will have a negative impact on your campaign’s performance. Your prospect might open the email but will probably unsubscribe immediately.
At Growbots we believe that the most effective previews are personalized, catchy and interesting enough, to make your prospect want to find out more.
