How to Write Compelling Email Subject Lines
With every email, there’s one very important piece of information that often seems to get overlooked: The Subject Line. The subject line of an email is one of the most important (if not the most important) detail that needs to be thought out carefully before sending. Why? Well, if your subject line isn’t intriguing or beneficial to the recipient, why would they open your email?
Lets just do the math:
Low open rates = Low click through rate = Low conversions/responses/visits = 
Most times, people write the subject line, as if they were either trying to sell something (This weekend: Save Big!), or writing an article headline (Local Committee Denies Claim). Do they work? Well, it depends. If you’re getting a response, than yes – but is your response the best you can achieve? The only way to truly know is through subject line testing.
Subject Line Testing:
Using A/B splits of your email are the most telling way of the success of your subject line. Quite simply, make two copies of your email, and change the subject line – send 50% with subject line A, and 50% with subject line B, while keeping everything else (time, day, email, content, copy, etc) the exact same.
After a week or two, pull the response numbers, and whichever garners higher conversions, is probably the better subject. (A week or two provides the most accurate measure, as more results will be in). Keep in mind, that just because Subject Line B pulls a higher open rate, doesn’t automatically mean its the best… Why not try out some more subject lines? You’re A/B split, can become an A/B/C/D/E/F/G/H split, if you think its justified – and in a lot of cases, it may just be.
Things to Consider:
Look at the style of your subject line, the phrasing, placement, and spam-ability. These all are factors to whether or not your email gets opened (or even seen) by the subscriber. Here are a couple examples below:
Example #1:
Subject Line A: BIG SAVINGS COMING SOON!
All caps starts raising red flags for spam filters, paired with an exclamation point, and the word ‘savings’, this one may SOUND great, but will it pull great? Not so much if it’s in your spam box.
Subject Line B: Save up to $50 This Friday
This may still come off as Spam because of the use of ‘Save’ and ‘Up to’, but is far more readable and offers a compelling offer (50$ off) and a deadline (Friday)
Example #2:
Subject Line A: Take a breathtaking hike in majestic Alaska this Summer from $48/person
This subject line sounds great, however, most email clients would begin to chop part of it off 5 or 6 words in. The reader may never see the subject line’s price, the season, or even the destination. While the subject line is actionable, it may get lost in the email clients.
Subject Line B: From $48/person, take a breathtaking Alaskan hike
This subject line offers the price right at the beginning, along with an action closely following. Assuming the recipient knows the sender (they did sign up to receive it, didn’t they?), the price may be a key factor in selecting an outdoor activity.
While these two examples don’t cover the broad spectrum of possibilities, it does show how you can test different lines to see how they respond. Some subject lines will pull better, some will convert better, and some will just fail. The ultimate way to tell is to try many different styles and phrasings, and see which one works best for you. While it does take a bit of time, be sure to keep track of the results and the subject lines, and eventually, you’ll find a pattern and style that works best for your email campaign.