Email Bounce Code Explanations

refer:http://help.sign-up.to/index.php/Email_Bounce_Code_Explanations

Sign-Up.to interpret email bounce codes in accordance with the RFC 3463 - Enhanced Mail System Status Codes Memo. While most email servers follow the same guidelines, some do differ, so explanations provided in this document and within Sign-Up.to applications should be considered an indication rather than an absolute truth.

Some email servers also send a brief explanation of the area along with the error code. Where this occurs, Sign-Up.to will show this additional information in the application. Due to the difference in interpretation of the guidelines, this addition information may not always agree with this documentation.

Bounce Codes

Codes are formed of three digits separated by periods. In the case of bounce errors, the first digit of these codes is either a 4 or a 5. A four typically means a persistent but not necessarily permanent error, where 5 is usually a permanent error. In the explanations below, Sign-Up.to treat errors beginning with 4 as soft, 5 as hard except where stated otherwise.

4.0.0 / 5.0.0

Undefined persistent error. Unfortunately some systems only issue general warnings such as this. As these error messages are vague, we treat them as soft bounces.

4.1.x / 5.1.x

Destination address error, usually caused by a bad address.

4.2.x / 5.2.x

Destination mailbox error, usually caused by a quota limit or other rule/error on the recipient’s server. Sign-Up.to treat all these errors as soft bounces.

4.3.x / 5.3.x

Destination mail system error or misconfiguration.

4.4.x / 5.4.x

Networking issues with intermediate or destination mail server.

4.5.x / 5.5.x

Mail delivery protocol status. This can be caused by any number of factors, from delivery mail server protocol errors to intermediate network issues or delays.

4.6.x / 5.6.x

Unsupported media or message content error.

4.7.x / 5.7.x

Security or policy status has triggered an error. It’s possible that an aggressive anti-SPAM policy or undesirable previous content has caused the system to reject mail. Sign-Up.to treat these as hard bounces so as not to further aggravate the destination mail server.

Acknowledgements:

RFC3463 - http://www.faqs.org/rfcs/rfc3463.html