Subject line real estate is precious. Make the most of it in your email campaigns.

Like most people​, I usually decide whether or not to open an email from a company depending on what the subject line says. I’d even go a step further and form an opinion about the company based on how they word their email subject lines and how consistent or unique they are with this as a branding activity.

Lately, I’ve noticed many companies trying to experiment with their subject lines. Here are a few important things I’ve learned from watching these experiments and trying out some of my own:

Short subject lines go a l​ong way

Depending on which email program your recipients use and their personalized display settings, they might not read a long subject. For example, my current display setting on Zoho Mail shows me the first 3-5 words of the subject.

The first few words are very relevant because those are the ones your recipient will almost always see. A recent study by Retention Science found that 6-10 word long subject lines tend to have the highest open rates. Keep your email subject lines short so they don’t get cut off.

Especially at an unintentionally awkward point:

“Summer’s here. Drown yourself in our soothing summer sorbet!”

“Summer’s here. Drown ​yourself…”

Oops! I’d just go with:

“Our soothing summer sorbet is here!”

After your email content is ready, spend some time thinking about subject ideas. List them down and shortlist a few that you like. Do an A/B test so the email that finally goes out to your entire mailing list is the one that has the best chance of being opened by them.

People are not merge tags.

OK, you’ve linked your email marketing software with your CRM so you already know a lot about your recipients. Good job! This can help you create customer segments right within your CRM, and send them customised campaigns based on the information you already have about them.

Merge tags are personalised fields that let you add dynamic customer info into your email subject or content.

Personalising your email subject with relevant merge tags can improve open rates. Note, however, that the key word here is “relevant”. For example, if I get an email with this subject line:

“Meera, here’s a special offer for you”

I know it’s a template which goes to an entire list and not really a special offer just for me. A subject line like this is a forced attempt at personalisation and is likely to be deleted. Similarly, the email subject “Check out what’s trending in New Delhi” might get my attention. But if the content of the email has nothing to do with New Delhi, it could be the last email I open from them.

A better way to do this would be to create customised versions of content for different segments of your audience. You can then use merge tags to personalise the subject for each segment. Some brands personalise the email content and the subject line based on the recipients’ browsing history. This can work really well providing the readers have given their consent to receive such updates.

For example, I like how TripAdvisor sends me hotel recommendations and pricing updates based on the places I’ve browsed through on their website. This adds some value, because they know I’m already interested in the places they emailed me about. The simple but subtly personalized subject lines are in sync with the customized content:

Langkawi holiday rentals from ₹6,119/night

Singapore or Kuala Lumpur? Where’s your next escape?

Cavelossim, Pulau Tioman or Alappuzha. Where will you go in 2014?

Also, they mentioned the places right at the beginning so the relevant parts of the subject don’t get cut off. Personalization makes a lot of sense when it comes with a layer of relevance built in.

When you use merge tags, make sure that they really do add a relevant personalized touch and not just because it’s one of the things you want to tick on your email marketing list.

Skip irrelevant information.

Some brands include content that doesn’t make any sense in the subject line. Here’s an example:

<planmytrip> <Thank you for your booking – Trip ID 3483548909088885435>

Skip information that means nothing to your reader. Focus on what really matters.

<planmytrip> <Thanks for booking your Delhi-London trip with us!>

Another thing that email marketers often miss: preventing the default header content from showing up in the preview text right after a short subject line.

“Can’t read or see email? View this message in a browser”

While the view in browser link is important for anyone who wants to view your email in a new browser tab, it shouldn’t necessarily appear in the preview area — particularly considering how email notifications show up on a phone for most people.

Solution: Include a preheader. A preheader is a relevant sentence about your email and should be placed right above the header text. If you only want this to show up after your subject and not in your email, just use a font color that merges with the background.

Creativity? Not everyone’s cup of tea.

I recently received an email from an e-commerce company. The subject line read:

“Don’t open this email!”

I was curious enough to click and discovered:

“Since you didn’t listen, and we’re glad you didn’t, here is a special discount voucher just for you.”

This is the point where I hunted for the unsubscribe link.

I’m not sure about the rest of their audience, but this certainly didn’t work for me. It felt cheesy, especially since I hadn’t shopped with them in a long time. If you want to be creative with your email subject, think through a few options that add elements like humor, mystery or surprise.

Here are some creative subject lines that caught my attention recently:

(From Digg) Does Heaven Have Wi-Fi?
(from Good.co) A how-to guide to becoming the office jerk
(From headhonchos) So, who will get the job?

Use a creative subject line only if you’re very sure it’ll work for your audience. Also, run the creative subject through an A/B test along with a safer subject. That way, you won’t risk jeopardizing the open rate for your entire email list.

Limited time offers work for a limited time.

Trying to catch your recipients’ attention with a limited time offer is a tactic that’s been done to death by most companies, especially in the e-commerce space. And yet, it works. But if you’ve been sending out a similar “limited time offer” every day or week, then remember these might stop exciting ​your audience after the first 999 offers. Okay, maybe much sooner.

So if you’re going to do this as frequently, stop calling it a limited time offer. Call it your offer of the week or deal of the month. Or give it a creative name that matches your brand. Whatever you do, limit the number of times you use this phrase in your subject line.

A good subject line can only take you so far.

And finally, if the rest of your email content is not in sync with your subject, your emails may never be opened again. Or worse, people might unsubscribe from your list.

Ensure that your email content is interesting and relevant. Ask yourself whether the email tells a good story about your brand or products — a story that can engage your readers with something new or valuable. If you have these things covered, experimenting with the subject line can definitely pay off.