By Research Fellow, Peter Slattery [updated 20/10/22]

At BehaviourWorks, we’re often asked: “Should we send emails or letters?”

There isn’t a right answer to this question – it always depends on the factors at play.

In this article, we explore some of these factors to help you to make better decisions. After that, we discuss persuasive strategies for written communication.

Comparing emails and letters

Letters and emails are different communication channels with different qualities.

To make these qualities clearer, let’s compare letters and emails in three ways:

• i) what they can do (that the other can’t),
• ii) how we engage with them, and
• iii) what they achieve.

What each can do (that the other can’t)

Compared to emails, letters can, for example:

• Reach target audiences that don’t have email.
• Have a tangible physical ‘presence’ that will hold attention for longer.
• People often keep letters for months, but process and discard emails very quickly.
• Gain appreciation or prompt a desire to reciprocate.
• Provide physical gifts and supplements alongside the information.

How we engage with them

Here are three relevant differences in how people engage with emails and letters.

First, when people open letters, they are usually focusing all attention on the letter. In contrast, when people open emails, they are more likely to be distracted. For instance, they may be aware of other emails on their screen.

Second, people have consistent expectations of the length of letters. Letters are usually one size. The letter-opener is therefore prepared to read a full letter when they get one. An unopened letter won't appear to be longer if we add a persuasive strategy. Usually it will be opened and read just as much.

In contrast, people vary more in their expectations of the length of emails. Short emails are common and emails don't come in a standard window, so their length is even more noticeable. If emails are longer, then the reader needs to scroll down the screen to get through them. The reader is therefore more likely to ignore or abandon longer emails.

Third, people open emails based on the source and subject line. People will be much more likely to read your email if it comes from a good and credible source, than if it doesn't. In contrast, letters give you much less information about who they are from or what they are about before they are opened.

How we measure their effectiveness

There are many different metrics for assessing how communication is performing. With letters, you can measure outcome factors, such as:

• Reception rate – did people get the letter?
• Open rate – did they open the letter?
• Recall rate – did they remember the letter.
• Response rate – did they respond to the letter?
• Compliance rate – did people do what the letter asked.

With email, you can often measure more outcomes, such as:

• Read rate – did they read the email?
• Read time – how long did they read the email?
• Click rates – how many people clicked a link?

In general, it is easier to measure metrics for email than for with letters. This is an important consideration for pilot-testing, monitoring and evaluation. For example, with email you can often track the percentage of intended receivers who:

• i) received the email
• ii) opened
• iii) engaged with
• iv) shared it, and
• v) acted because of it.

This is not usually possible with letters.

So, how do letters and emails compare when tested on similar outcomes?

Compared to emails, a higher percentage of letters are opened and responded to. But that doesn't answer our main question. We still don't know if letters change behaviour at a higher rate than emails.

What about cost-effectiveness?

Letters cost significantly more to send than emails, but do they return on that investment? There doesn’t seem to be a good research on this. However, some sources suggest that email is more cost-effective.

All the identified comparisons between letters and emails were quick summaries. All failed to control for confounding factors. We cannot therefore be sure that differences in outcomes were due to the channels used. Instead, they may be due to differences in the behaviours and populations targeted.

So, what are the implications?

These are some of the implications when choosing between letters and emails:

• It may be best to reserve letters for specific situations because letters are less cost-effective than emails. For instance, critical or time-sensitive communications, or cases where email cannot be used.
• It may be best to use email for complex and lengthy information because email makes it easier to direct readers to further information.

You can harness the benefits of both emails and letter by using both together:

• If you want to save costs, you can send a first wave of emails to prompt a response from all supportive parties. Then you can follow up with a letter to convert those who missed the email.
• If you have an urgent and well funded campaign, you can send letters and emails at the same time. This will ensure that as many people as possible are notified at least once.

Adding a persuasive technique to an email is somewhat riskier than adding it to a letter. The new content may be persuasive in insolation. However, the email’s increased length may cause potential readers to ignore the email or stop reading it. Be especially cautious if your email is already long or your readers are busy.

When writing emails, it becomes more important to think about what the receiver will see for the source of the email, and the subject line.

What are some persuasive strategies that can be used on email and letters?

At BWA, we developed a framework called INSPIRE. This framework make it easier to include persuasive strategies within written communication.

The INSPIRE framework outlines several techniques that improve the impact of written communication. Other frameworks, such as EAST, are also widely used.

Conclusion

So, should you send emails or letters? It still depends, but perhaps you now have a better sense of what it depends on – and why. What do you think of the letter and emails? What is your favourite behaviour change framework?

To learn about behavioural science, please check our other award-winning content, and free book. Please see this course if you are interested in learning more about INSPIRE.

To ask me to explore other behavioural science questions, please email: peter.slattery@monash.edu

References

1. https://www.smallbizgenius.net/by-the-numbers/direct-mail-statistics/#gref
2. https://www.tandfonline.com/doi/full/10.1080/0144929X.2019.1685594
3. https://www.billprint.com.au/mail-house/email-vs-direct-mail
4. https://www.snap.com.au/blog/research–direct-mail-vs-email—which-performs-best-5
5. Examining the online reading behaviour and performance of fifth-graders: evidence from eye-movement data