Why Are My Emails Bouncing?

An email bounce means your message was not delivered and was returned to you with an error message. Bounces fall into two categories: hard bounces and soft bounces.

Hard Bounces

A hard bounce is a permanent delivery failure. Common causes:

• The recipient's email address doesn't exist
• The domain doesn't have valid MX records
• The recipient's server has permanently rejected your domain

Remove hard-bounced addresses from your lists immediately - continuing to send to them damages your sender reputation.

Soft Bounces

A soft bounce is a temporary failure. Common causes:

• The recipient's inbox is full
• The receiving server is temporarily unavailable
• The message exceeded the recipient's server's size limit

Soft bounces may resolve themselves. Try resending after some time.

Reading Bounce Messages

Bounce emails typically include an error code and description. Common ones include:

• 550 - permanent rejection (often SPF/DKIM failure or blocked sender)
• 552 - message too large
• 421 - temporary server issue, try again later
• 451 - temporary local failure

What to Do

1. Read the bounce message carefully for a specific error.
2. Check that your SPF and DKIM records are correctly configured.
3. Verify the recipient's address is correct.
4. Check if your domain or IP is blacklisted.

If you're getting unexpected bounces, contact our support team for help reviewing the error details.