What is a soft bounce and a hard bounce in email?

When you send emails, some may fail to reach their destination. Understanding why an email bounced and what type of bounce occurred helps you keep your contact list healthy and improve your sending results.

What are the different types of bounces?

We differentiate between two types of bounces: soft bounces and hard bounces. Use the following tabs to learn what each type of bounce means:

🟠 Soft bounces🔴 Hard bounces

A soft bounce is a temporary delivery failure. When an email soft bounces, it means that, in most cases, the email address is valid and your email has reached the mail server of the recipient, but the mail server rejected it. It means that your email has not been delivered to the inbox of your recipient (or any of their folders, such as promotions or spam).

Here are some common reasons why an email address may soft bounce:

  • The mail server of the recipient is unavailable
  • The inbox is full (over quota)
  • The domain name doesn't exist
  • The email is too large
  • The email is blocked because of its content
  • The email cannot be relayed between mail servers
  • The email cannot be relayed because of unknown reasons
  • The email is blocked because of your sender or IP reputation

How does Brevo handle soft bounces?

Before an email soft bounces, it is deferred. At Brevo, we continue to attempt to resend the deferred email over the next 36 hours until the email is delivered. If it still remains undelivered after these attempts, we stop trying to send the email, and we mark it as a soft bounce in the campaign report or transactional report.

If an email campaign soft bounces five times consecutively, the email address of the recipient will be blocklisted. This does not apply to transactional emails.

Where can I find bounce details?

When an email bounces, mail servers usually provide the bounce error message to Brevo. This error message helps you identify the delivery error and understand why it happened by including:

  • The time and date when the email bounced
  • The mail server that bounced it
  • The reason for the bounce and error code

Follow the steps below to find the bounce error message for a specific contact:

Step 1: Segment the contacts who bounced

To view the bounce error message for a specific contact, you need to find which contacts bounced first. You can do this by segmenting them using the Email "classed as a soft bounce" or Email "classed as a hard bounce" conditions.

  1. Go to CRM > Contacts.
  2. Click Add filter.
  3. Select Marketing > Email > Email classed as "soft bounce" or Email classed as "hard bounce".
  4. Choose whether to look for any type of email, email campaigns, or transactional emails.
  5. Set the frequency condition and time range. For example, at least 1 time > over all time.
  6. (Optional) To filter by a specific email, click Choose which emails and set the condition to Email Name > Is exactly with the name of the email that bounced.
    email_soft_bounce_en-us.png

Step 2: View the bounce details

Once you have your list of contacts, you can check the exact error message for each one from their contact details page.

  1. From the segmentation results, click a contact to access their details page.
  2. (Optional) Go to the History tab and search for "soft bounce" or "hard bounce".
  3. Under a bounce event, click Show details.
    soft_details.jpg

The bounce error message is displayed. For example:

soft_message.jpg
💡 Good to know
Sometimes, mail servers don't provide a reason for the bounce. In this case, the reason appears as "unavailable".

What do the error codes in the bounce reasons mean?

The error code in the bounce message comes from the recipient's mail server, not from Brevo. Each mail provider uses its own set of codes and descriptions to explain why an email was rejected. Codes starting with 4XX usually indicate a soft bounce, and those starting with 5XX indicate a hard bounce.

Use the error code shown in the bounce details to look up the exact reason in your recipient's provider documentation:

Mail provider Error code reference
Gmail Gmail SMTP errors and codes
Microsoft (Exchange Online / Microsoft 365) Exchange Online non-delivery reports
Microsoft (Outlook.com, Hotmail, Live, MSN) Microsoft SMTP error codes
Yahoo Mail Yahoo SMTP error codes
💡 Good to know
For a corporate or custom mail server, contact the recipient's IT team and share the full error message. They will be able to investigate the rejection on their end.

Do I pay for bounced emails?

You only use your credits the first time we try to send the email. You are not charged when we try to resend the deferred email (before it soft bounces), and we never try to resend hard-bounced emails.

If my email bounces, do I get a refund?

If our platform encountered a technical issue that caused your emails to soft bounce, you may be eligible for compensation. Contact our support team by creating a ticket so that we can discuss your options. For any other case, compensation is not available.

🤔 Have a question?

If you have a question, feel free to contact our support team by creating a ticket from your account. If you don't have an account yet, you can contact us here.

If you’re looking for help with a project using Brevo, we can match you with the right certified Brevo Agency partner.

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