Email subject lines: one of the most hotly discussed topics in email marketing. How long should subject lines be? What’s more effective—all caps or lowercase? Are emojis cool, or annoying? The list goes on.

I think about these questions a lot as I’m editing SendGrid’s email subject lines and as I write my own. Fortunately, our Big Data Team has done some awesome analysis into Black Friday, Cyber Monday, and Valentine’s Day subject lines.

But I got to thinking, what about industry-specific subject lines?

Are there other factors that different verticals take into account when writing their copy? To answer my question, I decided to run a little inbox experiment, starting with the travel industry.

Now, this is not a super scientific experiment—I’m a writer for a reason. But I think the numbers below show enough trends for me to make assessments and to share some optimization tips to help the travel industry increase their overall email engagement—starting with subject lines.

The experiment

To start, I searched for the top travel sites for 2018 and created accounts for 4 of them (which will remain unnamed). I took no other action except to watch my inbox fill up for 3 weeks. After that 3 week period, here is what I found:

# of Travel sites I opted into: 4
# of Days analyzed: 21
Total number of emails received: 61
Emails in Gmail Primary Inbox: 7
Emails in Gmail Promotions Folder: 54
Average emails received per day from promotions folder: 3

(Note: For this subject lines analysis, I will only be looking at the 54 emails from the promotions folder.)

And here’s a minimized, scary look at my inbox:

Email subject line length

Of the 54 subject lines that I analyzed, the average word length was 8 (which is in line with our Big Data Team’s findings!). BUT, their research also showed us that 4 words in the subject line received the most opens and clicks. So travel sites are doubling that length with some reaching as high as 17 words! In fact, a third of the subject lines I received had double-digit subject lines.

Average = 8 words
High = 17 words
Low = 3 words

Take a look at how these long email subject lines look on mobile—half of them are cut off! With over 55% of your recipients viewing their emails on mobile, brevity is key!

Optimization tip: Keep it short, travel! The mobile view of my inbox is overwhelming. Too much text can bury your lead and detract from engagement. Don’t put all of your information in the subject line, leaving no reason for recipients to open your email. If you want meaningful engagement, you need to be strategic with your subject line copy.

For example, if you’re offering a discount in your email, test simply teasing it in your subject line, and not giving it all away up front. e.g. “New discount inside…” “More destinations just a click away.”

It can be a challenge to fit all of your enticing info into a 3 or 4-word subject line. So don’t feel like you need to immediately jump from an 8-word subject line to half that, but test your way into it. Remember—you want to encourage your recipients, not overwhelm them. Double-digit subject lines might be doing just that.

Personalization: my name was used in 14/54 subject lines.

I hate to say this (and I do give these travel sites credit for using what little information they had about me), but using your recipient’s first name in the subject line is kind of like subject line 101, no? Seeing my name in a subject line doesn’t grab my attention. In fact, in my opinion, it does the opposite. It feels advertorial instead of personal. And no one wants that!

Optimization tip: If you don’t have any other recipient data to go off of, this is when you should spend extra time on crafting creative and compelling subject lines. Don’t take the easy way out. I think most of us would rather see copy that appeals to our curiosity (or our wallets) than seeing validation that a sender knows our first name.

Consider getting straight to the new discount alert or travel destination you’re showcasing—clear and concise.

Or, try being upfront about not having a ton of your recipient’s info and ask them for more details in the subject line instead. Something like, “Hey, we’d like to know more about you…” Or “We want to send you relevant deals” and then have the body copy prompt your recipient to go to your preference center to complete their profile. That feels more recipient-focused and genuine than just using their first name, right?

And if you DO have additional information about your recipients in regards to location, past purchase behavior, etc. use it meaningfully and not as a sales pitch. For example, say I used one of these travel sites to book a trip to Miami last year—something like this would be fun and thoughtful:

“Show Miami who’s boss again”
“Miami wants a rematch”
“Miami says ‘Double or Nothing’”

Subject Line emojis: emojis appeared in 8/54 subject lines (about 15%)

I was actually surprised to not see more emojis in my inbox. There was a lack of palm trees, airplanes, or fruity cocktails! It seems like these travel senders have either already tested different emoji options or they saw that our Big Data Team found that during Black Friday and Cyber Monday only 3.6% of senders are using subject line emojis and that they tend to not help with engagement.

Optimization tip: Emojis may work for you, but proceed with caution. Test out emojis if they fit with your brand, but if not, the wisdom of the recipient crowd is telling us to keep those subject lines clean and clear!

Capitalization: There was very limited “shouting” throughout my inbox

Thanks, travel! All caps were used sparingly and only to convey urgency, just as they should be. I applaud the travel sites here for being tasteful and strategic with their all-caps use. Keep it up!

Email frequency: I received 54 promotional emails in 21 days, which is about 3 emails per day.

If my calculator is serving me correctly, at that rate across 4 senders, I’m receiving about 20 emails a month from each sender! According to our 2018 Global Email Benchmark Report, the aggregate send rate across industries is 7 per month. In this experiment, travel is putting that average to shame!

I’d maybe feel differently if I were actually engaging with the emails I received, but, not a single one of these senders noticed that I wasn’t even opening their emails during my 21-day experiment! That’s a red flag to pump the breaks and ask me if I want to adjust my communication preferences.

Optimization tip: Listen to your recipients! If they’re not engaging, make a change!

Takeaways

Of all the tips and findings above, I think the greatest trend that I saw was that all of the subject lines I received from these 4 senders were pretty similar! Take a look at the sample in the subject line length section above and see if you feel the same? I’m not sure I could look at any of the subject lines and match them with the brand that sent them.

So the takeaway here is: differentiation is key. Travel senders, how are YOU going to stand out from the other senders in your industry? The fight for the inbox is REAL. If you want to get those clicks and opens, get back to that keypad and start thinking outside of the box!

For more inspiration on perfecting your email marketing campaigns beyond just subject lines, check out SendGrid’s best practice guide, The Essential Guide to Email for Travel and Hospitality. 



Jillian Wohlfarth
As SendGrid's Director of Content, Jillian is responsible for ensuring that SendGrid provides valuable thought leadership content through the blog, whitepapers, webcasts, and more. When not writing and editing, you can find Jillian frequenting Denver restaurants in search of the best queso.