Symantec Messaging Gateway (SMG) uses Simple Mail Transfer Protocol (SMTP) response codes to provide feedback about email delivery issues. These codes help administrators understand why emails were delayed or rejected and identify the necessary steps to resolve them. This article summarizes common SMTP response codes generated by SMG, grouped into temporary and permanent errors, with links to detailed explanations for each code.
Temporary errors, also known as soft bounces, indicate transient issues that may resolve without intervention. However, if these errors persist, they require further investigation.
Permanent errors, or hard bounces, indicate issues that prevent delivery and require corrective action to ensure successful email transmission.
Note: For additional troubleshooting, you can refer to the below article:
Troubleshoot email delivery issues using telnet