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Mobile optimization is a must, but do your customers even want to open your emails on their phone? Your mobile subject line is your foot in the door.

A lot of customers open emails on mobile platforms. No news there. Before we can think about rendering issues and fat-finger syndromes, we have to get our emails opened in the first place. Your subject line could make or break your campaign. It takes your customers 3 seconds to decide what to do with your email, can you afford to end up in the Trash folder?

Do I need to worry about mobile?

The latest email client statistics from Litmus show a 5% increase in email opens on mobiles, standing at 48% of all opens.

You should check your own statistics too. Check your web analytics and your email stats to see which platforms and browsers your visitors and subscribers are using. You’ll probably find mobile is accounting for a larger and larger share.

Mobile subject lines

The Email Marketing Holy Trinity

The first things your mobile recipients see are the from line, the subject line and the preheader text. You need to make sure you optimise this trio. I get lots of emails with the Preheader ‘This message has no content’ and ‘If you can’t read this email, click here’. This a waste of space so don’t let your customers doubt the chance they gave you. Even if they decide not to open your email, this trio should still be consistent with your branding.

Mobile-friendly subject lines

The biggest difference with mobile subject lines is that you have less space to impress. Most smartphone email apps will only show between 20-30 characters. So make your impact fast (and Samsung Galaxy SII will show only 11 characters in landscape mode – gasp!). If you  can’t make your subject line that short, make sure you capture the attention in the first 20-30 characters.

Looking at the Adestra Subject Line Report, you can see how different words in your subject line influence the open rates. You can get an overview, or even choose one of the six sectors we researched: B2B publishing, B2C Publishing, B2B Events, B2C Events, Charities & Not for Profit and Retail & Ecommerce.

Let’s take some examples. Showing benefits works really well, so including keywords like ‘available’ and ‘new’ will boost your open rate by 28.3% and 23.2%, respectively. Being timely and relevant also helps with ‘alert’ scoring +38.1% and ‘weekend’ +13.2%.

Now let’s look at some industry specific stats.

In Retail & Ecommerce, including the words ‘free’ and ‘cheap’ will devalue your brand (-33.7% and -63.2% open rates), but ‘sale’ ranks well with +10.7%. However, ‘latest’ scored a whopping +95.4% and ‘free delivery’ +35.9%. We all love a free delivery, don’t we?

Show me tell me

Based on our research, here are some example of mobile subject lines that could work:

Retail: ‘New glow-in-the-dark charms’
News: ‘Daily: April Fools vs Real News’
Events: ‘Don’t miss: free tickets to Marketing Week Live’

But don’t just take my word for it, test, test, test! And try our Subject Line Checker as a little guide.


  1. Keep mobile subject lines short and sweet (20-30 characters)
  2. Make your from line, subject line and preheader work together for your brand
  3. Look at our Subject Line Report to see what works in your own industry