13 Factors Leading to Low Email Deliverability Rate & Their Fix!

The true value of an email campaign lies in its ability to land in the recipient's inbox.

Despite best efforts, achieving this seemingly simple goal is not easy, especially with billions of emails sent every day – Many emails end up in spam folders, or worse, get blocked entirely.


This damages the sender reputation, intensifying future email deliverability issues and making it difficult for marketers to succeed in their outreach campaigns.

Before we dive into what factors can cause your email deliverability rate to drop, let’s clear the air about email delivery and email deliverability.

'Delivered' refers to emails that are successfully transferred to the recipient’s mailbox provider, but this doesn't guarantee they reach the inbox.

'Deliverability,' on the other hand, measures the percentage of emails that actually make it into the inbox, often tracked through open-and-click statistics. Without high deliverability, email marketing efforts can become a significant waste of time and resources.

Watch this video to understand what is email deliverability & its importance in detail.

The path of an email to the intended recipient’s inbox involves a complex process with three key players:

Here's a breakdown of the journey:

Sending the Email: When we hit the send button, the email then passes through several ISP checks and filters. At this point, the email is considered "delivered," but it has not yet been confirmed whether it has reached the recipient's “inbox”.

Email Transmission: The email message is formatted using the Simple Mail Transfer Protocol (SMTP) for transmission over the Internet. The recipient's mail server looks up the domain portion of the receiver's email address on a Domain Name System (DNS) server to determine which Mail Exchanger (destination mail server) should be contacted to deliver the message. Both the sending and receiving servers use the SMTP protocol to transmit the message.

Authentication: The sender's server adds authentication protocols such as SPF, DKIM, and DMARC to verify the legitimacy of the email and reduce the likelihood of it being marked as spam.

Receiving the Email: Lastly, the recipient's server accepts and delivers the message. It is then received using standards like the Internet Message Access Protocol (IMAP), which allows the recipient to download and read the email.

Understanding these steps helps ensure that your emails reach their intended destinations. Now that we have covered the basics, let’s get back to the whys and hows related to a good email deliverability rate.

Here's why maintaining a good email deliverability rate should be a top priority for your email marketing efforts:

To summarize, a good deliverability rate ensures your emails reach their intended audience, maximizing engagement and campaign ROI. It also protects your sender's reputation, preventing future emails from getting flagged as spam.

Depending on your industry and the platform you use for sending emails, the deliverability rate also varies. It typically ranges from 88% to 99%. To ensure you're on track with your email deliverability, pay attention to the following metrics:

Remember, while reaching 100% is ideal, it's not always achievable. So keep a close eye on your campaign performance, and good email practices to work towards a strong deliverability rate.

If you are experiencing an email deliverability issue, you may notice some of the following signs:

Now, let’s move on to learn about the factors affecting your email deliverability and what could you do to fix the issue.

Here are a few major reasons your email deliverability rate might be going down the graph.

Purchasing email lists is a common but harmful practice that significantly lowers email deliverability rates. Additionally, recipients on these lists are not familiar with your brand, increasing the likelihood of your emails being marked as spam.

High bounce rates can damage your sender's reputation, while increased spam complaints can result in your emails being blocked or filtered into spam folders. There are also chances that ISPs might blacklist your email domain or IP address, further reducing deliverability.


💡 Quick fix:

Not verifying emails before adding them to your email list is a mistake that can cause severe damage to both your database quality and campaign performance. When you accept unverified emails, it means you are letting in the bad emails too.

These might include invalid, inactive, disposable, and fake email accounts. Sending emails to such addresses will result in high bounce rates that negatively affect your sender's reputation, making it more likely for your future emails to land in spam.

💡 Quick fix:

As already mentioned a bad sender reputation can occur due to high bounce rates, spam complaints, and sending to inactive subscribers.

Poor sender reputation can lead to emails being filtered into spam folders, ISPs may throttle your email sending, delaying delivery, and in extreme cases, your email domain or IP address may be blacklisted.

💡 Quick fix:

Missing email authentication methods like SPF, DKIM, and DMARC can severely hinder email deliverability. These authentication protocols are essential for verifying the sender’s identity and ensuring emails are not being sent by malicious actors.

Without proper authentication, your emails may be marked as spam or fraudulent. Moreover, unauthenticated emails are more susceptible to being spoofed by phishers, which can further damage your sender reputation and erode recipient trust.

A recipient marking an email as spam is the strongest negative signal to mailbox providers about your email. Complaint rates above 0.2% are considered high and may result in poor deliverability.

In the case of mailbox providers, like Gmail, a spam rate of more than 0.1% can start to affect your deliverability, which is why you need to keep a close eye on it.

A lot of factors affect your complaint rates. Some of them include incorrect domain names; getting flooded with too many emails; Irrelevant and too lengthy content; a difficult process for opting out of emails. All of these can annoy recipients, putting you in serious trouble.

💡 Quick fix: