Email Subject Line Best Practices

Ever wonder how to get email recipients to open your emails? It’s simple – original, catchy, and well-crafted subject lines. According to Optinmonster, 47% of emails sent are opened and 69% of emails are marked as spam by recipients based on the subject line alone. Gain subscribers with quality content to ensure better open rates, conversions, and inbox placement. Help email recipients grasp your brand and business with these effective strategies determined by Idealgrowth.

A/B testing

If sending emails on a regular basis is a common practice, consider A/B testing. Test similar subject lines or messages on numerous occasions to see which subject lines generate the most responses. One example of A/B testing is to take a smaller percentage, ex: 30%, of your subscriber list and split the percentage into two. 15% will receive email A and 15% will receive email B. Whichever email performs better out of the two will be sent to the remaining 70% of subscribers. Pinpoint phrases, keywords, or offers to optimize your email marketing formula. Continuously using this strategy over time will boost open rates and results. 


Subject lines are there for a reason. They serve as the introduction to your email and your message. A nuanced subject line informs the recipient exactly what they will find in the actual email. The subscriber can misinterpret an unspecific or unrelated subject line and email. Misleading the subscriber incites negative responses if the recipient believes you are delivering the wrong message. You potentially run the risk of subscribers marking future emails as spam or unsubscribing altogether. Clear messaging ensures trust from recipients and high deliverability rates.


First impressions with the right content and presentation are everything. Attract the audience you want by resonating with their expectations. Does your brand and audience reflect a level of professionalism? Consider using proper punctuation. Is your brand more carefree? Use a balance of lowercase letters and emojis. Regardless of what audience you are reaching out to, correct spelling and grammar is always a must.


Believe it or not, recipients open emails if the subject line contains a specific keyword. Studies done by email marketing agency Alchemy Worx analyzed 21 billion emails sent by 2,500 brands, and on another occasion reviewed an additional 24.6 billion emails. Similarly, Adestra and Smart Insights analyzed billions of emails and reported their findings. Across all studies, the words new and wonderful were the top keyword contenders for high open rates. A/B testing over time can help determine which keywords your subscribers respond best to.


More users prefer to check email on their phones as opposed to other devices. Make sure your subject lines, pre-header messages, and email templates are optimized for the small screen. Call to actions and short, easy-to-read text show the best results. Free marketing tools like Zurb’s TestSubject allow you to test subject lines to see how they will appear on a mobile device.


Email recipients are 10-14% more likely to open an email if the subject line is personalized to them. Including the subscriber’s first name or using friendly and inviting copy in the subject line are effective practices to boost open rates. Segmentation, a prospecting software tool that selects a certain audience to target, is also a great practice to hone in on.


Psychological factors are important and compelling tools for engaging an audience. No subscriber wants to feel like they’ve missed out on a great deal or offer. Limited availability and limited time frames imply scarcity and urgency. Keywords such as alert, urgent, limited, short time, important, and hurry in are proven to reel in subscribers to check out the email or take further action. Open-ended subject lines act as cliffhangers that elicit subscribers to open the email out of curiosity. Asking questions, dropping hints, and promising tips are good practices you can set in place. Lastly, using pain points and offering a solution to a problem for subscribers will guarantee opens. Examples of pain points are “Stop wasting money on products that don’t work” or “How to get through the busy holiday season.” In effect, you can tailor your email’s content to provide tips, offers, and exclusivity subscribers will treasure and look forward to the next time you send out an email.


Grab recipient’s attention by writing effective retargeting subject lines. Retargeting emails are sent to subscribers who did not complete an action or sale. Strategies include reminding and alerting subscribers of what they are missing out. Offering a new or better deal helps to retrieve a subscriber and entice them to take another look.