Glossary -
Email Deliverability

What is Email Deliverability?

Email deliverability is the ability to deliver emails to subscribers' inboxes, considering factors like ISPs, throttling, bounces, spam issues, and bulking. Achieving high email deliverability is crucial for the success of email marketing campaigns, as it directly impacts whether your messages reach the intended audience. This article will explore the fundamentals of email deliverability, its importance, the factors affecting it, and best practices to improve and maintain high deliverability rates.

Understanding Email Deliverability

Definition and Concept

Email deliverability refers to the success rate at which email messages are delivered to the intended recipients' inboxes. It is a measure of how well an email marketer can avoid their messages being marked as spam or being blocked by internet service providers (ISPs). Deliverability focuses on ensuring that emails not only reach the recipients but also land in their primary inboxes rather than in the spam or junk folders.

The Role of Email Deliverability in Email Marketing

Email deliverability plays a pivotal role in email marketing by:

  1. Ensuring Message Reach: Guaranteeing that emails reach subscribers' inboxes.
  2. Increasing Engagement: Maximizing the chances of emails being opened and read.
  3. Protecting Sender Reputation: Maintaining a good sender reputation to avoid being flagged as spam.
  4. Optimizing Campaign Performance: Improving overall email marketing metrics such as open rates and click-through rates.
  5. Building Trust: Establishing and maintaining trust with subscribers and ISPs.

Importance of Email Deliverability

Maximizing Reach and Engagement

High email deliverability ensures that your messages reach the maximum number of subscribers. When emails land in the inbox rather than the spam folder, the likelihood of subscribers opening and engaging with the content increases significantly.

Protecting Sender Reputation

Maintaining a good sender reputation is essential for email deliverability. A poor sender reputation can lead to emails being blocked or marked as spam. Consistently high deliverability rates help protect and enhance your reputation with ISPs and subscribers.

Optimizing Email Marketing ROI

Achieving high deliverability rates directly impacts the return on investment (ROI) of your email marketing campaigns. By ensuring that your messages reach the intended audience, you can maximize the effectiveness of your campaigns and achieve better results.

Building Subscriber Trust

Consistently delivering relevant and valuable emails to subscribers helps build trust and credibility. When subscribers trust that your emails will be delivered reliably and contain valuable content, they are more likely to engage with your messages and remain loyal to your brand.

Factors Affecting Email Deliverability

Internet Service Providers (ISPs)

ISPs play a significant role in determining whether your emails reach the inbox or are filtered as spam. Each ISP has its own set of rules and algorithms for filtering emails, and maintaining a good sender reputation with ISPs is crucial for high deliverability.


Throttling refers to the practice of ISPs limiting the number of emails that can be delivered to their users within a specific timeframe. Sending a large volume of emails too quickly can trigger throttling, resulting in delayed or blocked emails.


Bounces occur when an email cannot be delivered to the recipient's inbox. There are two types of bounces:

  • Hard Bounces: Permanent delivery failures due to invalid or non-existent email addresses.
  • Soft Bounces: Temporary delivery failures due to issues such as a full inbox or temporary server issues.

Spam Issues

Spam filters are designed to protect users from unwanted and potentially harmful emails. Emails that contain certain keywords, have suspicious formatting, or come from unknown senders may be flagged as spam and redirected to the junk folder.


Bulking occurs when an email is delivered to the recipient's bulk or spam folder rather than the primary inbox. This can happen due to various reasons, including poor sender reputation, suspicious content, or lack of engagement from recipients.

Best Practices to Improve Email Deliverability

Maintain a Clean Email List

Regularly clean and update your email list to remove invalid, inactive, or unengaged email addresses. This practice helps reduce bounce rates and improves overall deliverability.

Actions to Take:

  • Use double opt-in to confirm subscribers' email addresses.
  • Regularly scrub your list to remove hard bounces and inactive subscribers.
  • Implement re-engagement campaigns to win back inactive subscribers or remove them from your list.

Use a Reputable Email Service Provider (ESP)

Choose a reputable ESP that has strong relationships with ISPs and a proven track record of high deliverability rates. A good ESP will provide tools and features to help you manage your email campaigns effectively and maintain high deliverability.

Actions to Take:

  • Research and select an ESP with a good reputation and positive reviews.
  • Utilize the deliverability tools and features offered by your ESP.
  • Monitor your deliverability rates and address any issues promptly.

Authenticate Your Emails

Email authentication helps verify that your emails are coming from a legitimate source. Implementing authentication protocols such as SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) can improve your deliverability.

Actions to Take:

  • Set up SPF to specify which mail servers are allowed to send emails on behalf of your domain.
  • Implement DKIM to add a digital signature to your emails, verifying the sender's identity.
  • Use DMARC to specify how your domain handles suspicious emails and receive reports on email authentication.

Monitor and Improve Sender Reputation

Your sender reputation is a key factor in email deliverability. Monitor your reputation using tools like Sender Score or your ESP's reporting features and take steps to improve it if necessary.

Actions to Take:

  • Avoid sending emails to invalid or inactive addresses.
  • Ensure your email content is relevant and valuable to subscribers.
  • Monitor your email metrics and address any issues that may negatively impact your reputation.

Optimize Email Content

Crafting high-quality, relevant, and engaging email content can significantly improve deliverability. Avoid using spammy language, excessive punctuation, and all caps, which can trigger spam filters.

Actions to Take:

  • Personalize your emails to make them more relevant to your subscribers.
  • Use a clear and compelling subject line that avoids spam triggers.
  • Ensure your email content is well-formatted, with a balanced text-to-image ratio.

Engage Your Subscribers

High engagement rates signal to ISPs that your emails are wanted and valued by recipients. Encourage subscribers to open, read, and interact with your emails to boost engagement.

Actions to Take:

  • Send relevant and personalized content that resonates with your audience.
  • Use segmentation to target specific groups of subscribers with tailored messages.
  • Include clear and compelling calls to action (CTAs) to encourage interaction.

Test and Optimize Email Timing

Sending emails at the right time can improve open rates and engagement. Use A/B testing to determine the best times to send your emails and adjust your sending schedule accordingly.

Actions to Take:

  • Test different sending times and days to identify the optimal schedule for your audience.
  • Monitor the performance of your emails and make data-driven adjustments.
  • Consider time zones and global audiences when scheduling your emails.


Email deliverability is the ability to deliver emails to subscribers' inboxes, considering factors like ISPs, throttling, bounces, spam issues, and bulking. Achieving high email deliverability is crucial for the success of email marketing campaigns, as it directly impacts engagement, sender reputation, and overall campaign performance. By maintaining a clean email list, using a reputable ESP, authenticating emails, monitoring sender reputation, optimizing email content, engaging subscribers, and testing email timing, you can improve and maintain high deliverability rates. Implementing these best practices ensures that your messages reach the intended audience, fostering stronger relationships and achieving better results in your email marketing efforts.

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