Symbolically Sinking – 10 Findings on Symbols in Subject Lines

Two years ago I wrote a blog post on the use of subject line symbols. At the time, I made the point that the approach was more effective when the use was intentional – using them to provide an indicator of content or message type, for example.

There is clearly still a lot of interest in this topic. Screen sizes are getting smaller, and senders are being challenged to fit more information into less space.

With Valentine’s Day just gone (think loads of emails with ♥ symbols in them!) it seemed like a good time to re-visit the subject. I asked my colleagues to send me their Valentine’s emails, and then used Return Path’s Inbox Insight data to analyze effectiveness.

Here’s the top findings:

  1. On average, the use of symbols is driving disengagement

Some of the most common subject line symbols included ♥, ✈, ☰, ⌛, and ☼. The overall Read rate for emails using these symbols was lower than for the overall index:

Criteria    Read rate (Index = 100)
  Subject line uses symbols 100
  Subject line does not use symbols 110

This finding aligns with broader research I have carried out, and suggests that continued use of symbols contributes toward subscriber fatigue.

  1. Having a “theme” is more effective

The good news for those of us who are still romantics at heart is there are exceptions to disprove the rule! Valentine’s Day emails using subject line symbols (mostly ♥) outperformed those that didn’t.

 Criteria  Read Rate (Index=100)
 Valentine’s emails without  symbols  100
 Valentine’s emails with  symbols 116

Previously, I suggested that use of symbols is more effective when they reinforce the theme being promoted. These findings appear to confirm this – subscribers could easily identify the emails in their inboxes containing Valentine’s Day offers

  1. The use of symbols does not cause increased spam filtering

Some email practitioners have avoided using symbols in case they caused increased spam filtering. However, this appears to be unfounded:

 Criteria ISP Filtered Rate (Index=100)
 Spam filtering rate without symbols 100
 Spam filtering rate with symbols 67

The level of spam filtering for emails with symbols in their subject lines is actually ± 1/3 less then where they were not used.

  1. Symbols generate greater recognition in the spam folder!

An unexpected learning was that subscribers appear more likely to retrieve emails from their spam folder when subject lines contain symbols:

 Criteria      Not Spam (Index=100)
 Voted “Not Spam” (no symbols)                 100
 Voted “Not Spam” (used symbols)  401

This is a highly desirable behavior. Mailbox providers consider “Not Spam” notifications to be a powerful indicator of subscriber engagement.

I should caveat this result by noting the relatively small sample size. However, it does suggest that perhaps symbols make emails more visible when subscribers are scanning their spam folders for the ones they want to retrieve. Also – where subscribers sort their folders by subject line, symbols will appear before alphanumeric characters.

  1. It’s all about positioning

Where the symbol is positioned in the subject line also impacts effectiveness. Is Prezzo’s approach, where the symbol is the first character (“♥ Valentine’s reminder | Book now”), more effective than Swarovski’s where it is further in (“Free ♥ key ring │ Classic sparkle for your Valentine”)? The results suggest that – like being a good dancer – it’s important to lead!

 Criteria  Read Rate (Index=100)
 Symbol is first character  116
 Symbol in not first character                 100

First is clearly good. This probably talks to the way people scan when they read. If symbols are used, they need to be the first thing seen to maximize effectiveness.

  1. More is possibly better

Similarly, are multiple symbols like Tesco (“♥ Half-price Champagne ♥ Meal deal for two ♥ Plus top deals on wines you love”) more effective that The Warehouse’s single-use approach (“❤ Loving the value this Valentine’s Day”)?


 Criteria                                          Deleted Without Opening (Index=100)
 One symbol used  100
 Multiple symbols used  81

Read rates weren’t significantly different. However, Deleted rates are lower when more than one symbol is used. This is important – Deleted Without Opening rates are considered a negative engagement metric by mailbox providers.

  1. Know your audience device profile

Understanding how subscribers engage with their emails influences the successful use of subject line symbols. Consider the following example from Expedia:





Research from Mailchimp shows mobile users are much better targets than those using Hotmail/Outlook. Return Path customers can use Email Client Monitor to identify which subscribers will likely be most receptive.

  1. Be careful not to overdo it!

We have also watched with interest as Ryanair pushes the limits of subject line symbols usage. Recent eye-catching examples include:

  • Winter Getaway from £19.99 ❄✈
  • Summer Fun from €24.99
  • >>–❤–> Get ready for V-day!

Which is well and good until the emails are sent to accounts that don’t support these symbols, resulting in the following:

  • Winter Getaway from €19.99 ️❄️��
  • Summer fun from €24.99 ��������
  • >>–❤–> Get ready for V-day! �������� ����

Now perhaps Ryanair is on top of its game, because Read rates where symbols are used are slightly higher than when not the case, suggesting the approach resonates positively. However, we recommend rigorous testing before deploying similar examples with your own programs!

  1. Don’t look spammy

With the prevalence of email fraud, legitimate senders need to be careful about not doing anything to make their emails look spammy, which could erode confidence of subscribers. Using financial symbols (“Fly from £9.99. Save ? for when you get there!”) is a common approach by spammers.

As an aside, senders should also consider other indicators of spamminess such as spelling, grammar, and incorrect case conversion. For example:

  • Return Path vs return path, Returnpath or return-path.
  • Sender Score vs senderscore
  • DMARC vs dmarc

This lack of attention to detail can compromise trust, creating reduced engagement as a result.

  1. Get optimizing

None of these findings are absolute, and may well vary depending on context. However, each example represents an incremental performance opportunity, and illustrates how Return Path’s data, tools, and expertise can be leveraged to deliver Email Optimization for your email programs.

Recent research from Experian shows the average amount earned for each delivered email is $0.09 (£0.06/€0.08). Based on an average open rate of 17.1% we can infer a value per open of $0.53 (£0.35/€0.48).

If you have an email list of 1 million addresses, and sending once per week, optimizing your program performance to deliver just 1% uplift in average open rates will generate $275,000 (£180,000/€250,000) in additional ROI.

That kind of uplift symbolizes why you should give the C to showing some to your email program so, you can make more‘, which in turn will make your stakeholders

Get optimizing now!

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