An introduction to email deliverability

Table of contents

1. What is deliverability and why does it matter?
2. How is deliverability determined?
3. Sender reputation
4. Subscriber engagement
5. Content
6. In summary
7. Frequently asked questions

What is deliverability and why does it matter?

Deliverability is a measure of how many of your emails land in your subscribers' inbox rather than the spam folder. After all the work you put into your email marketing, you want to be sure that your messages are actually seen by your subscribers! That is why deliverability is fundamental.

How is deliverability determined?

Many factors influence inbox placement. Broadly speaking, email providers try to determine three things:

1. Is the message safe?
2. Is the message wanted by most subscribers?
3. Is the message wanted by this particular subscriber?

If the answer to all three questions is yes, the message belongs in the inbox. If any of the answers is no, the message will end up in the spam folder. To make that decision, email providers rely on the sender reputation they have calculated for you.

Sender reputation

Email providers such as Gmail, Microsoft, Yahoo and so on create a reputation score for your sending domain. You can think of it like a credit score, but unfortunately there is no single source that can tell you exactly what your score is and why.

Email providers keep both your score and the algorithms used to determine it private. However, the most important deciding factor is how subscribers engage (or fail to engage) with your messages.

Subscriber engagement

The best way for email providers to determine where your emails belong is to observe how your subscribers interact with them. There are actions your subscribers can take that will increase your sender reputation, and others that will lower it.

List health

• Only import subscribers who have given you direct permission to receive marketing emails. Quality matters far more than quantity in email marketing.
• Protect your forms with double opt-in and/or ReCaptcha. If your form is not secure, bots are likely to start abusing it, damaging your deliverability.
• Clean your list regularly. Make sure you do not accumulate "cold" or inactive subscribers. If you do not clean your list, unengaged subscribers will become the majority, lowering your reputation and sending more messages to spam.

Consistency

An important component of your sender reputation is consistency. Any sudden change in the way you send messages can be seen as a risk by email providers, who may move your emails to the spam folder.

• Sending domain: It is perfectly fine to send from several domains, but make sure the domain you use is recognisable to subscribers. Avoid sending from a brand-new domain or from one that has not sent email for a long time (more than 6 months).
• Volume: Try to send to a consistent number of subscribers each week. It is normal for your list to grow or shrink, but avoid large swings in volume (for example, going from 5,000 to 20,000 subscribers overnight).
• Frequency: Send at least once a month to keep your reputation stable. If providers do not see enough email from you, they will not be able to maintain a reputation for you. At the same time, do not send too often and annoy your subscribers.

Content

Although content matters far less than it once did for inbox placement, it can still affect your deliverability, especially if your sender reputation is not well established.

If email providers do not have enough data on your consistency, they may rely on content to decide whether your message is safe and wanted. Here are a few things to keep in mind:

• Do not use link shorteners: Because they are often used by spammers, they can trigger spam filters. Transparency is the key to good deliverability.
• Spam words and phrases: The biggest mistake is using excessively promotional and/or urgent language. Try to write emails that sound human and conversational.
• Image-to-text ratio: There is no magic number, but a good guideline is to have enough text for the message to be clear even if the images do not load.
• Avoid gimmicks: A subject line such as "Re: Your order #2095642" might increase opens in the short term, but it will cost you your subscribers' trust.
• Encourage genuine engagement: Give your subscribers permission to interact with you authentically. This will not only improve your reputation, it will also build a relationship with them.

In summary

Good deliverability comes from putting subscribers first: building a clean, engaged list, sending consistently and creating valuable content. This helps email providers trust you and deliver your emails to the inbox rather than to spam.

Frequently asked questions