How to Write Email Subject Lines That Get Opened

In this tutorial, we’ll review the importance of email subject lines and discuss the principles that can make the difference between emails with strong open rates and those that spend too much time in the spam box.

Importance of the Subject Line

The email subject line determines the likelihood of whether an initial email is opened, ignored and/or filtered into spam. Honing this imperative skill will ensure that you command more “opens”, putting more eyes on important offers and content, building better relationships, and yielding more revenue.

Slight Increase in Open Rates, Big Impacts on Revenue

Improving major email communication channels can have a massive impact on responsiveness and, ultimately, your bottom line.  Let’s look at a basic example that compares how a slightly increased open rate affects responsiveness in an initial email sequence.

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We’ll start with five emails in an initial sequence, and an average 20% open rate.  These emails are sent to 1,000 prospects, resulting in 1,000 opened emails. If the click-through rate is 25%, there will be 250 visits to the company site. With a 5% purchase or appointment rate, the company yields 12 sales or appointments.

Now, if we begin with the same five email sequence that has the same text content, but we attune the subject lines according to best practices, we instead average a 33% open rate.  Instead of 1,000 opened emails, we end up with 1,165 opened emails. If the same 25% click through rate is maintained, we see 416 visits instead of 250. Keeping with the same numbers and the 5% purchase or appointment rate yields 20 sales or appointments, almost double the yield based on a small tweak in the subject lines.

Relevance (Marketer’s Perspective)

Relevant email subject lines is a big leverage point that is often overlooked. Overcoming these initial potential barriers and bottlenecks changes the game, and mastering the skill of attuned email subject lines is imperative. Some initial points to consider:

  • Think like a marketer.  Deliver messages to a prospect that makes them think, “This is for me”.  Emails need to resonate and get a prospect to relate.
  • Different groups of people respond differently. Demographics matters, and so does the relevance of the business of industry. If the product is related to green technology, or the service to healthcare, be specific and include this language in the subject line – it’s likely going to increase email open rate.
  • Segment by customer goal. If a customer visits your site and is able to select their goal for your product or service from a dropdown menu. For example, a prospect entering their email address on an auto repair website may be interested in updates about (a) detailing and cleaning, (b) parts and equipment, or (c) regular oil changes and tune-ups. Is a prospect looking for a regular place to take their auto in for monthly check ups?  If you’re an auto repair shop, use this information in your subject line (appealing to the expressed goal of the prospect is an almost guaranteed way to lift response rate).
  • Segment by lead source. If you just offered a webinar and received a list of registrants, try including ‘webinar registrants’ in the first 3 words of the email subject line.  Offering a spring discount? Use that language in your email subject line.  Offering a deal just for existing customers? You get the picture.

Relevance and flagging, either per situation, state, season, etc., help increase the open rate, our number one priority.

“Red Flags”

There are a number of “red flags” that can make the difference between emails opened and emails filtered to the spam box.  Here are a few to watch out for:

  • All CAPS. Three letters (think abbreviations) or more in a row is riding the line. Occasionally this tactic might be worth the surprise factor, but in general its a negative and a spam risk.
  • FuNky caps or $ymbols.  These are always a spam risk and should be used sparingly, if at all. The $ symbol is an almost guaranteed spam boot.
  • ‘Free’, ‘Only’ or ‘100%’. Type in ‘spam filter words’ and these invariably come up every time.  Again, use very sparingly, if at all.  Also, avoid any use of the ! symbol, if possible.

Are all of the above off limit at all times?  Not necessarily. None are guaranteed to result in an email being filtered, but just keep in mind that including one of the above is likely to increase the percentage of getting sent to spam by a landslide.

Length of Subject Lines

A brief note on length of subject lines. Unfortunately, there exists no magic algorithm. In general, subject lines should stay between 6 – 10 words and under 140 characters.  Also, short, 1 – 4 word email subject lines should be used sparingly i.e. “Check this out” or “New deal inside”.

Common Errors to Avoid

A few email subject line common errors to avoid:

  • Using same subject line repeatedly.  Try calling or labeling the event something slightly different each time.  There is some value to consistency, especially if an event happens monthly or quarterly, but use identical language and open rates are likely to drop.
  • Irrelevant initial emails. Again, relevance to customers is a deal breaker. An email subject line of “New coupon code for new customers” is likely to result in the reaction, “Who is this and what is this?” When you first acquire an email address, either through a purchase or opt-in, make sure to include the name of business, or the specific product, or the website where the customer recently visited. Acknowledge the customer connection, and do so in a timely fashion.
  • Using prospect’s first name in subject line for every email. By the second email, the relevance of the ‘customer’s first name’ strategy is gone. Use this one sparingly.
  • Caps & symbols (again).  Go back and comb through those scheduled email subject lines and remove excessive symbols and caps.

Stick to these Principles

Take away these best practices, and you’ll see increases in your initial email open rates:

  1. Use any tactic sparingly for best results i.e. once a month, or once every two months.
  2. Draft 3 – 4 subjects lines before deciding on which email subject line to send. If sending a five-email automated sequence for new customers, think through which subject line will hit home and is most relevant to the customer.
  3. Stick to 6 – 10 words in subject lines, and stay under 140 characters.
  4. Flag various list segments with emails that call out to the specific customer i.e. past customers, location, etc.

If you follow the email marketing business audit process (which we outline in this previous video blog), you may find many of the common errors that we’ve outlined here today in your own marketing sequences or newsletters. This can be valuable “low hanging fruit” to lift your ROI on email marketing.

Remember, effective email subject lines are just of many tools that you can use to turn email marketing into a money maker for your business.

– Daniel Faggella
CLVboost Founder
About The Author

Daniel Faggella

I grow businesses with marketing automation, email marketing, and conversion-rate optimization. I’ve spoken on business and emerging technologies internationally and at some of America’s finest schools (Yale, Stanford, Cornell, etc…). My marketing strategies have been featured in the Boston Business Journal, MarketingProfs, Direct Marketing News, and much more. CLVboost is where I share marketing strategies, TechEmergence.com is my major pursuit.