Email Subject Line Best Practices to Improve Your B2B Open Rates

By Andy Mowat | Updated: 27 Jan, 2015
“64% of People Say They Open an Email Because of the Subject Line”
– Chadwick Martin Bailey

When deciding on a subject line, you must first gain clarity on the purpose, email content, and audience. From there, a set of best practices should flow.

We have strong opinions on email subject line best practices for inter-office communication, but I'll save that for another post. This post is about best practices for subject lines in your mass-email marketing blasts used for business networking.

Email Subject Line Best Practices to Improve Customer Email Open Rates

It should come as no surprise that email subject lines do in fact impact email open rates.

Busy professionals and executives receive hundreds of unsolicited emails on a daily basis; at a glance, they must use time management best practices to decide which emails they deem worth their time to open and read while the rest end up deleted. Unfortunately, subject lines are often an afterthought in email marketing—in reality, businesses should be spending more time crafting engaging email subject lines.

I can’t tell you for certain how to consistently create engaging email subject lines, but I can give you a list of common best practices to try out for improving them.

Just remember, best practices are not rules, they are guidelines!

Length does matter, in most cases

Although the rules can change depending on industries, many studies and tests have proven that shorter is better. Especially if you consider that up to 66 percent of ALL emails are opened on mobile devices with smaller screens that typically cut off subject lines longer than 50 characters (4 to 7 words); this percentage is according to one study conducted by Moveable Ink’s Q1 2014 US Consumer Device Preference Report.

“RE” and “FW” are powerful, but not alone

Yes, according to some studies, emails with “FW” or “RE” in the subject line will increase your email open rates by as much as 92 percent, mainly because it implies the email is coming from a trusted source. Not only is this practice misleading, it will also make your business look desperate.

Be clear

Without giving too much away or being too wordy, try to communicate what is in the email to allow the reader to prioritize the message and not be confused when they open the email. For instance, if you need a response or have a deadline for follow-up, it’s okay to put this in the subject line.

Capture your reader’s attention

Subject lines don’t always need to fully describe what is in the email. They just need to entice someone to open the message. Therefore, think of how to offer value and incentivize the reader to dig deeper.

Be personal, but not too personal

Help your reader see that the email isn’t a spam message—rather, convey that it is something that appeals directly to the reader by including personal details in the subject line. Words like ‘you’ and ‘your’ let your readers know there is an actual person sending the email that understands their needs and interests.

Don’t sell

There is nothing busy people hate more than salesy or spammy emails. This is not to say that you can’t sell in your email. Just try to avoid sounding like a run of the mill sales email by including certain words like “free,” “last chance,” “explode your business,” and “discount.” These might seem like they create urgency, but in fact can make your email sound like a sales pitch. This approach has been proven to reduce, rather than increase, open rates. Not to mention the fact that certain words like “free” might trigger a spam filter.

Don’t be repetitive

If you are sending an outreach email or newsletter on a regular basis, be sure to vary your subject lines regularly. The last thing you want to do is bore your readers with the same subject line week after week that reads “This week’s newsletter.”


Okay, maybe we’ve grabbed your attention here—but in an email setting, this format just isn’t polite. Using capital letters and explanation points is the equivalent of jumping up and down, waving your arms, and yelling! You wouldn’t talk this way to your customers face to face, so don’t do it in your emails.

Test, test, test

As you focus on creating the best email subject lines possible, remember these are general rules and best practices. There isn’t a one-size-fits-all answer to crafting the best email subject line. The best way to truly know what resonates with your audience and ensure you are achieving your highest open and click through rates for all your email campaigns is to combine your efforts with A/B testing, also known as split testing.

As you try out different methods to contribute to your business growth strategies, you might be surprised to discover what works and what doesn’t.