Email deliverability is the process for getting an email delivered into a recipient’s inbox. It is broken down into two main areas; delivery and deliverability. Before reading on It's worth understanding what happens when you send a campaign.

1. Delivery refers to whether a receiver’s server accepts your email.
2. Deliverability or Inbox Placement refers to where that message ends up once it is accepted; in other words, the inbox, spam folder, or if it is silently deleted.

It is important to understand that there is a very clear distinction between the two and different rules apply to each.

Delivery

An email that is considered delivered simply means that it has not bounced or been returned by the mail server. The email has got passed the first gate. This does not consider what happens to the email afterwards i.e. whether the email ends up in the inbox or spam folder.

If your email is rejected at this stage the server will send us a bounce message with a code. We can then classify why the email was rejected. You can read more about bounces here.

Deliverability

Deliverability refers to where your email ends up once it has been accepted passed the first gate. There are three parts to deliverability:

1. Authentication and Identification

These are the various elements that prove you are who you say you are when you send an email: SPF, CRP, DKIM, and DMARC. They are the email equivalent of a passport that proves your identity and that you are legitimate. It's like registering your car to your driver's license. Anyone who did a check on the car would know that you drive it. If they found someone else driving your car, they'll know they shouldn't be doing so.

2. Reputation

Reputation is the level of trust you have as a sender. Reputation can be earned by demonstrating good sending behavior. It can, on the flip-side go down if you demonstrate poor practice.

• Examples of good sending behavior:
  • Only sending to contacts who are engaged (i.e. opens & clicks in the past 12 months)
  • Sending more relevant content to contacts based on their interests (e.g. Preferences Form)
  • Better timed emails based on historic data and/or more consistent sending (e.g. same days of week / same time of day)
  • Use email design best practice to increase engagement in current database
  • Rule of Thumb: Better engagement (i.e. opens & clicks) = better inbox placement
• Examples of poor practice:
  • Sending to old and/or non-engaged contacts (i.e. No opens or clicks in the past 12 months)
  • Sending with a very high frequency to non-engaged contacts
  • Sending to contacts who did not opt-in to receive your emails

3. Content

The content of your email including copy, URLs and subject line can affect your deliverability. Though this has become less important in recent years.

Although, using best practice in email design can help maximize engagement which positively affects your sender reputation. You can find best practice tips in our Email Design and Creative Guide.

A simple analogy

Imagine you work for FedEx and are delivering a letter to an office building. You go to the reception desk and hand the letter to the receptionist (the receiving server).

• They tell you that the person on your letter does not work there or no longer works there. As far as FedEx is concerned this letter has not been delivered. (Bounced) Or,
• They accept the letter and sign for it. As far as FedEx is concerned the letter is delivered (accepted by the receiving server).

The receptionist then has many options they could follow.

• The letter looks a little bit dodgy and they aren’t sure that it is legitimate. They keep the letter on their desk and let the recipient know that they’ve received something dodgy which they could collect if they want. (Spam)
• They’ve seen these letters before and know that the recipient doesn’t want them so they decide to throw away the letter and not say anything to the intended recipient. (Silently deleted)
• They see that the letter has come from a reputable company because the letter is branded accordingly and they deliver the letter to the recipient. (Inbox)

Ensuring that your emails end up in the inbox is not an exact science. The organizations and systems that filter emails do not openly give information on their algorithms. Unfortunately, this does leave us to guess at the reasons why an email has ended up in the spam folder. There are so many different levers that cause deliverability problems that it is almost impossible to pinpoint the exact reasons.

Fortunately, there are some best practices to follow and pitfalls to avoid. Read more about how you can avoid ending up in the spam folder.

If some of the terms in this article are unclear you can see a glossary of terms here.

Next: What happens when you send a campaign