Top 5 Best Practices for Email Subject Lines

Today’s post is written by Katy Creates, PR Manager at ContactMonkey, a smart email tracking for Outlook, Gmail and Salesforce, based in Toronto.

How long do you spend on writing the perfect email subject line? 10 seconds? 10 minutes? 10 hours? New research suggests that you are wasting your time.

Email tracking service, ContactMonkey, has analysed over 30 million emails to find out what works best for their users. It is the first time anyone has ever collected this amount of data.

They have now released their research on the best performing email subject lines specifically to help salespeople convert those leads into wins.

1. When in doubt, worry less

Time spent thinking about the perfect subject line is time wasted. There is no perfect subject line. Just a simple Re: got a 92% open rate according to the research.

2. Be direct

Longwinded marketing speak fared very badly. It might work for a blog post but your subject line should act as a taster, not the main course. As an example, a long subject line like: “10 secrets for accelerating business results” achieved only a 10.92% email open rate.

3. Use less words

Do you know what device your lead is reading your email on? It’s almost impossible to tell unless you start using a service like ContactMonkey. The service tells you when your email is opened, where the recipient is in the world, what links they clicked and what device they read the message on.

Did you know that 40% of the time the first time a person reads your email it will be on a mobile device?

That’s why the next piece of advice is so important. Keep your subject line short,very short. Nothing more than 3 words is ideal. An average mobile device can fit 4-7 words across the screen but the best performing subject lines were 1-3 words.

4. Don’t ask

The research showed that questions in email subject lines fared particularly badly. Perhaps because a question can make it look like a marketing email. If you’re a salesperson you don’t want to be lumped into the spam folder. Key to sales success is building a personal relationship. So keep your subject lines simple and personable.

5. Use technology

If you really want to write the best email subject lines you have to learn from your mistakes. There is a whole raft of email tracking software readily available that you can download and use to optimise your emailing habits. There is no good reason not to do this. Collecting solid information on which email subject lines are opened the most, what devices your leads are using to read your emails and what time of day they open them is invaluable data that simply was not available to salespeople a few years ago. Try a few out and find out what works best for your business and your clients.


Infographic authored by ContactMonkey, an email tracking service
for salespeople
. To view the
original post, see the original subject line infographic.
  • Chris Hemphill

    All the top-performing subject lines contain “Re:.” Are there numbers that show those same subject lines performing just as well without the “Re:” component? I’m curious because the article mentions a tremendous sample size of 30 million e-mails, but it does not specify whether these were initial contact e-mails or if it also included subsequent e-mails based on conversations initiated.

    Additionally, were you able to gather data on response rates?

    If possible, I’d be very interested in seeing whether there’s any correlation between word length in the body of the message and positive responses or opportunities generated.

    Thanks for providing this information!

    • Katy Creates

      Hi Chris, thanks so much for your reply. I’m glad you found our research useful!

      ContactMonkey analysed data from every email we tracked in order to gain this insight, this includes initial contact emails and subsequent communications, however we can certainly look at aggregating the data further in order to find out that detail.

      We also don’t track the content of the email, so we couldn’t comment on which call to action is most effective. What we can say is what email subject lines work best, in most cases. And as with all research the best takeaway you can get is a general confirmation that long email subject lines fare poorly, whereas short subject lines perform much better. I hope this helps.

      Perhaps the best way to find out which email practices work best for your business needs is to download ContactMonkey yourself and analyse your own data over the course of a few months? Let us know how you get on!

    • charlesbronson

      I try not to open ANY “re:” emails unless this is a response in conversaion. This is a spam marker to me. If you start with “re:” you will most likely still get high open rate but this is not what the e-mail is about – it’s about the end result. When I open “re:” email and realize it’s just a trick to make me open it I dump it wihout reading