The ultimate guide to mastering email deliverability


How to improve deliverability? Think like an ISP

If you want to improve your email deliverability, you need to think like the people that make email possible: the Internet Service Providers (ISPs). To do that, you need to understand the scope of what ISPs deal with every day.

Question: how many emails are sent globally each day?

Any guess?

It’s in the neighborhood of 270 billion, give or take a few billion. A little more than half of those are business emails, while a little less than half are consumer emails.

Reflect on that number for a minute. Then reflect on the fact that that’s a daily number.

Now, what percentage of those 270 billion emails are spam? Would you believe that it’s about 50%? It’s true – over 100 billion spam messages are sent every day.

It’s a true tidal wave of spam, trying to make its way to your (and everyone else’s) inbox. 

ISPs are excellent at managing this neverending onslaught of spam. They make sure spam doesn’t even make it to your spam folder, let alone your inbox. By doing so, they’ve positioned themselves as heroes to email recipients.

But to do their task, they need to be a bit ruthless.They need to punish bad sending habits. Put yourself in their shoes. They’re dealing with massive volumes of emails from malicious senders. Would you act differently?

If you want your emails to be delivered, try to think like an ISP. Remember, they know the history of your mailing list. They know which emails have been clicked and which haven’t. They know the last time someone opened one of your emails. And if no one is clicking on your emails, you can bet you’ll wind up in the spam folder…or not even delivered at all.

What is the objective of email deliverability?

This question might seem too simple. The objective of email deliverability is to get your email delivered, of course. But it’s not so simple.

Let’s say your latest emailing evaluation report says you have a 99% deliverability rate. Sounds good, right? 

But deliverability rate can be misleading. It’s missing one important point.

You don’t want to just get your email delivered. You want to get your email to your customer’s inbox.

The true goal of email deliverability is to get good inbox placement.

Email that winds up in a customer’s spam or junk folder is still considered to be delivered. Delivery rate tells you nothing about inbox placement. Don’t be fooled by high delivery rates. Focus on inbox placement.

How do you get good inbox placement? To answer that, you need to understand the full journey of an email.

The journey of an email

Email Deliverability - The Journey of an email

You’ve created a new email as part of your Black Friday campaign. Who will you send it to? Let’s walk through the steps.

1. Step: You build your mailing list.

Distributed email

This is everyone you target for an email.

2. Step: You send your email.

Sent email

Most of your email will actually get sent. Some, however, will be suppressed, meaning there is no attempt to actually send them.Why? There could be a few reasons. Maybe they’ve revoked their consent. When your ESP prepares to send the mail, they evaluate consent, and the email is suppressed for that address.

3. Step: Your sent mail is delivered.

Delivered email

From the emails that are successfully sent, most of them should be delivered (meaning they get to where they’re supposed to go). Those that aren’t either soft bounced or hard bounced.

Bounced Email: Why Wasn’t My Email Delivered?
Soft BounceHard Bounce
Full inboxSudden increase in sending volumeFrequency too high for engagement levelsEmail address does not exist or is invalid

What’s a Hard Bounce?

hard bounce means that you tried to send an email to an invalid address (one that doesn’t exist). If you get lots of hard bounces, it’s a signal to ISPs that your mailing list isn’t very clean. You can clean up your list by doing an email validation.

What’s a Soft Bounce?

soft bounce can occur for a couple reasons. In the past, you might get soft bounced if you try to email someone with a full inbox. These days, most email service providers offer much larger inboxes, so this is rarely the reason for a soft bounce.

Most soft bounces today occur when there is a sudden increase in email sending volume. If you typically send 500,000 emails per day, then one day suddenly send 700,000, those extra 200,000 emails might be soft bounced. ISPs like consistency, and don’t like sudden changes.

4. Step: Your delivered email makes it to the inbox…or not.

Inbox email

From the emails that are delivered, many will end up in the inbox. The ones that don’t either go to a spam folder, are blocked by the receiver, or hit a spam trap.

What’s a Spam Trap?

spam trap is an unmanned email address, owned by an ISP. This email address might be an abandoned one that’s been reclaimed by an ISP, or it might be a brand new address created solely as a spam trap. Either way, it shouldn’t be on your mailing list. If you send an email to a spam trap, it has a big negative impact on your sender reputation. In fact, hitting a lot of spam traps is one of the worst things you can do for your sender reputation. Don’t worry though, you can minimize your risk.

5. Step: Emails in the inbox are either opened and unopened.

Opened email

When is an Email Considered Opened?

How can you know an email has been opened if you’re not actually watching over someone’s shoulder? Most modern email service providers include a very small image in emails they send, called a tracking pixel. When someone opens their email, that loads the image (which requires a request to be made to the server that hosts the image). This request lets the email service provider know that the email has been opened.

6. Step: Finally, the recipient takes some action with the email.

Clicked email

Let’s look at the actions, and what they mean for you:

  • Clicked. Your customer clicked on something in your email. This shows engagement, and is probably what you’re hoping they’ll do with your emails.
  • No click. Not great news for you, but also not too important for the ISPs. Really low engagement is a signal that you need to work on your content. Try to increase personalization.
  • Unsubscribe. Also not the best news for you, since you’ve lost a contact. But ISPs understand that people’s preferences change, and an unsubscribe won’t have a large negative impact on your reputation.
  • Mark as spam. ISPs take this seriously. You definitely want to avoid lots of spam complaints. Customers might mark you as spam if it’s hard to unsubscribe from your emails, so make it easy for customers to unsubscribe. You also want to make your consent page easy to navigate – if customers get confused or lost in your consent page, they’re far more likely to just mark your email as spam and be done with it. Respect your customers and make it easy for them to unsubscribe.

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