Optimize your email deliverability

Do your emails reach the recipients' inboxes, or do they bounce? Are your emails received properly by the receiving domains—is your communication considered to be wanted?

Most of your emails will get through to the recipients' inboxes but from time to time, some emails will have problems getting through. The receiving domains and you have the same thing in common: the recipient. You want to send communication to your customers and the receiving domain wants to make sure that only proper communication gets through to the recipient. Briefly, this is email deliverability.

The key for optimizing your email throughput is to understand how the process works and how to respond correctly. Sometimes you will get blocked for the wrong reasons and sometimes the reasons will be valid. This guide will provide you with the key information on how to optimize your email communication from a delivery perspective. But remember—whenever you need help in any way, please contact us.

Why do not all emails reach the inbox?

Generally, and simply put, it's because your communication is considered unwanted for a given reason. This doesn't necessarily mean that you're sending unwanted emails to your recipients, just that the receiving domain is considering your emails to be so. The reason can be that your communication is spam-like and the IP address you are sending from is blocklisted and/or that you don't have enough engagement amongst your recipients. The ISP* will look at all these variables and decide if you are a desired sender.

Let us look a bit more into the factors that affect inbox placement.

*ISP = Internet Service Provider or Inbox Service Provider. In this case, we use ISP as a collective term for the companies providing the email services e.g., Gmail Outlook Live and Yahoo.

Recipient engagement

How active are your recipients? Are they engaging by opening the emails? How often do they open? The ISPs are constantly monitoring the engagement and it is your task to keep up engagement levels. Here are some pointers:

  • Segment your emails and send relevant information
  • “Listen” to your recipients. If they are not engaging, ask yourself why. What is your sending frequency, what are you offering and why should they engage. What's in it for them?

List hygiene

Always make sure that your list only contains proper opted-in contacts. This is pretty much list hygiene in a nutshell. Don't force in new email addresses in the lists through negative opt-in or vague opt-in terms. Be very clear with your subscribers regarding what they can expect from your communication.

Ensure that the email addresses you have in your lists are confirmed by using confirmed opt-in:

  • Double opt-in through confirmation email
  • Dual fields for entering email address
  • Email address validation in forms

By practicing good list hygiene, you are also taking steps towards avoiding spam traps.

Spam Traps

A spam trap, also known as honey traps, are a way for ISPs to understand and evaluate the quality of a senders list. The trap itself is an email address that acts like a real address but doesn't exist. There are different types of spam traps, and they all indicate that you don't have proper list management. 

  • Pure or Pristine – Addresses created by the ISPs to identify spammers as the only way you can obtain these addresses is pretty much by scraping the addresses yourself or through bought lists. As a sender with proper opted in addresses, you cannot hit a spam trap like this.
  • Recycled – Older and previously inactivated email addresses that are re-used as spam traps. These used to be real addresses but as the holder of the email address stopped using them, some of them can be converted to spam traps.

Spam traps are of course hard to avoid all together as different customer segments has different level of digital presence. One rule of thumb is trying to understand the activity level of your recipients and using that to "clean up the list". Now, over to Opens.


Why "Opens" and not "Open Rate"? While "Open Rate" indicates a general activity level, looking into the opens gives you a better picture which of your recipients are active and which are not.


IP reputation is measured by different services using different metrics and depending on how well your email communication is considered to be, your IP is scored, often from 0–100 or bad/good.

The reputation score (good/bad, 0–100) can give you an indication on how well your IP is performing but there is not one global internet IP reputation so this should not be seen as the only truth when it comes to deliverability. The score is rather an indication of how you are generally performing.

The large ISPs such as Gmail, Outlook Live and Yahoo use even deeper analysis to evaluate your reputation. They are also measuring subscriber activity as an important parameter. If your subscribers are engaging in your emails, you're getting a higher credibility. 

Some examples of engagement are: 

  • One subscriber is opening emails often
  • Different subscribers are opening different send-outs
  • The subscribers are moving the emails to the inbox from the campaign/spam folders
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