Email bounce

An email bounce occurs when a message cannot be delivered to the recipient’s inbox and is returned (or “bounced back”) by the receiving mail server. Bounces are typically categorized as:  

Soft bounces: Temporary delivery failures, often due to:  

• Recipient’s mailbox being full  
• Server downtime or throttling  
• Message size limits  
• Reputation-related rejections  

Hard bounces: Permanent delivery failures, such as:  

• Invalid or non-existent email addresses  
• Malformed email syntax  

High bounce rates are a signal to inbox providers that your list quality or sending practices may be poor, which can damage your sender reputation and reduce deliverability.  

To reduce bounces, maintain a clean list, validate addresses at sign-up, and monitor bounce codes in your email logs.