Soft vs. Hard Bounces

When an email cannot be delivered to an email server, it's called a bounce. The email server will generally provide a reason for the incident, and Mailchimp uses those reasons to determine how to treat that email address. We categorize bounces into two types: hard bounces and soft bounces.

In this article, you’ll learn about hard and soft bounces in Mailchimp.

Beginning February 2024, Gmail and Yahoo will require a custom authentication and a published Domain-based Message Authentication, Reporting & Conformance (DMARC) record for anyone sending more than 5,000 emails to Gmail or Yahoo addresses in a 24-hour period. To prevent your emails from bouncing, we strongly recommend authenticating your email domain and configuring DMARC.

Also, if you use a free email service like Gmail or Yahoo for your From email address, we strongly recommend you switch to an email address from a private domain, like the one you use for work or for your website.

For more information about custom authentication and DMARC, check out About Email Domain Authentication.

Things to know

Here are some things to know.

• Mailchimp can't predict whether or not an email will bounce.
• The receipts for your bounces will be available in your email reports for 30 days after the email is sent.
• Different internet service providers (ISPs) bounce email messages based on their own rating systems and definitions.

Hard bounces

A hard bounce indicates a permanent reason an email can't be delivered. In most cases, hard bounced email addresses are cleaned from your audience automatically and immediately. Cleaned addresses will be excluded from all future sends. Here are some common reasons an email may hard bounce.

• Recipient email address doesn't exist.
• Recipient email server has permanently blocked delivery.

There are occasionally cases in which valid email addresses will hard bounce.

Soft bounces

Soft bounces typically indicate a temporary delivery issue and are handled differently than hard bounces by Mailchimp. When an email address soft bounces, it will immediately display as a soft bounce in the email report.

If an email address continues to soft bounce, the address will eventually be considered a hard bounce and cleaned from your audience. We'll allow 7 soft bounces for an email address with no subscriber activity and up to 15 soft bounces for contacts with previous subscriber activity before converting a soft bounce into a hard bounce. While there are many reasons an email address may soft bounce, these are some of the most common.

• Mailbox is full (over quota).
• Mailbox isn't configured correctly.
• Mailbox is inactive.
• Recipient email server is down or offline.
• Recipient email server has been sent too many emails during a period of time.
• Email message is too large.
• Domain name does not exist. This may be a temporary issue.
• Email message blocked due to content.
• Email message doesn't meet the recipient server’s policies.
• Email message failed DMARC.
• Email message doesn't meet the recipient server’s anti-spam requirements.
• Email message doesn't meet the recipient server’s anti-virus requirements.
• Email message doesn't meet the recipient server’s sender requirements.
• Email can't be relayed between email servers.
• Email can't be relayed for unknown reasons.

Next steps

Now that you know what hard and soft bounces are, you can view bounce details in your email report. It's a good idea to keep a close eye on your bounce rate to be sure your emails are reaching your contacts. This can help you to abide by spam laws and avoid bounce suspensions.

About Email Reports
Causes of High Bounce Rates
Anti-Spam Requirements for Email
About Email Domain Authentication
About Bounce Suspension
Verify an Email Domain