As an email marketer or sender, it's crucial to understand the different types of email bounces that can occur. Bounces indicate when an email fails to reach its intended recipient. By understanding these bounce types, you can identify and address delivery issues, improve your email campaigns' effectiveness, and maintain a healthy sender reputation. In this comprehensive guide, we'll explore the various email bounce types, their causes, and how you can effectively handle them.

Table of Contents

  1. <a href="#soft-bounces">Soft Bounces
  2. <a href="#hard-bounces">Hard Bounces
  3. <a href="#transient-failures">Transient Failures
  4. <a href="#mailbox-full-bounces">Mailbox Full Bounces
  5. <a href="#block-bounces">Block Bounces
  6. <a href="#spam-complaint-bounces">Spam Complaint Bounces
  7. <a href="#how-to-handle-bounces">How to Handle Bounces

<h2 id="soft-bounces">Soft Bounces

A soft bounce refers to a temporary delivery failure where the email cannot reach the recipient's inbox at that particular moment. Soft bounces are typically caused by temporary issues, such as:

  • Recipient's mailbox is full
  • Recipient's email server is temporarily unavailable
  • Email message is too large to be delivered
  • Temporary network or connectivity issues

Soft bounces indicate that there is a chance for the email to be delivered successfully in the future. Email service providers usually retry sending the email to the recipient's address for a certain period before categorizing it as a hard bounce.

<h2 id="hard-bounces">Hard Bounces

A hard bounce refers to a permanent delivery failure where the email cannot be delivered to the recipient's inbox and is returned to the sender. Hard bounces are typically caused by permanent issues, such as:

  • Invalid or non-existent email address
  • Recipient's email server has blocked the sender's domain
  • Recipient's email server has marked the sender as spam

Hard bounces indicate that the email address is invalid or no longer exists. It's essential to remove hard bounced email addresses from your mailing list to maintain a clean and engaged subscriber base.

<h2 id="transient-failures">Transient Failures

Transient failures occur when there is a temporary issue during the email delivery process, causing the email to be delayed or not delivered at that moment. These failures are often due to factors such as:

  • Recipient's email server is experiencing a temporary overload
  • Temporary network or server issues
  • Recipient's mailbox is temporarily unavailable

Transient failures are similar to soft bounces as they indicate a temporary problem that may resolve itself. However, it's important to monitor these failures and take appropriate action if they persist.

<h2 id="mailbox-full-bounces">Mailbox Full Bounces

A mailbox full bounce occurs when the recipient's email inbox has reached its storage capacity, preventing new emails from being delivered. This bounce type typically indicates that the recipient needs to free up space in their

mailbox to receive new messages.

If you receive a mailbox full bounce, you can try reaching out to the recipient through an alternate communication channel to notify them of the issue.

<h2 id="block-bounces">Block Bounces

Block bounces occur when the recipient's email server or a spam filter blocks the incoming email due to various reasons, such as:

  • Sender's IP address or domain is on a blacklist
  • Email content triggers spam filters
  • Email authentication issues (e.g., SPF or DKIM failures)

If you encounter block bounces, it's crucial to review your email authentication setup, check for blacklisting issues, and ensure your email content complies with best practices to improve deliverability.

<h2 id="spam-complaint-bounces">Spam Complaint Bounces

Spam complaint bounces occur when a recipient marks an email as spam or junk. These bounces indicate that the recipient is not interested in receiving emails from the sender or considers them unsolicited or unwanted.

To minimize spam complaint bounces, maintain proper email list hygiene, ensure recipients have opted in to receive emails, and provide relevant and valuable content to your subscribers.

<h2 id="how-to-handle-bounces">How to Handle Bounces

Handling email bounces effectively is essential for maintaining a good sender reputation and improving email deliverability. Here are some recommended actions to take:

  • Soft Bounces: Monitor soft bounces and retry sending to the addresses over a certain period. If the bounces persist, consider removing them from your mailing list.
  • Hard Bounces: Immediately remove hard bounced email addresses from your mailing list to prevent further delivery attempts. Continuing to send emails to invalid addresses can harm your sender reputation.
  • Transient Failures: Monitor transient failures and consider re-sending the emails after a short period. If the failures persist, investigate the root cause and take appropriate action.
  • Mailbox Full Bounces: Reach out to the recipient through an alternate communication channel and request them to free up space in their mailbox. You can attempt sending the email again once they have cleared their mailbox.
  • Block Bounces: Review your email authentication setup, check for blacklisting issues, and ensure your email content aligns with spam filter guidelines to reduce block bounces.
  • Spam Complaint Bounces: Take spam complaints seriously and investigate the reasons behind them. Ensure you have obtained proper consent from recipients and provide a clear option to unsubscribe from your emails.


Understanding the different types of email bounces is crucial for effective email marketing. Soft bounces indicate temporary delivery issues, while hard bounces represent permanent failures. Transient failures, mailbox full bounces, block bounces, and spam complaint bounces each have their own causes and implications. By handling bounces appropriately and maintaining a clean mailing list, you can enhance your email deliverability, engagement, and overall campaign success.


What is a bounce in email marketing?

In email marketing, a bounce refers to the failure of an email to reach its intended recipient's inbox. Bounces can be categorized into different types, such as soft bounces and hard bounces, each indicating different causes and implications.

How can I reduce email bounces?

To reduce email bounces

, consider the following:

  • Maintain a clean and updated email list by regularly removing invalid and inactive email addresses.
  • Use double opt-in to ensure subscribers provide valid email addresses and consent to receive emails.
  • Implement proper email authentication (SPF, DKIM) to improve deliverability and reduce the likelihood of being marked as spam.
  • Create relevant and engaging email content that resonates with your audience to reduce spam complaints.
  • Regularly monitor email bounces and take appropriate action, such as removing hard bounces from your list.

What is the difference between a soft bounce and a hard bounce?

A soft bounce is a temporary delivery failure where the email cannot reach the recipient's inbox at that moment, often due to issues like a full mailbox or temporary network problems. A hard bounce, on the other hand, is a permanent delivery failure caused by factors like an invalid or non-existent email address. Soft bounces indicate a chance for successful delivery in the future, while hard bounces indicate that the email address is no longer valid.