When messages bounce or fail in either the On-Demand service or in an On-Premise system, failure codes are provided in order to indicate the nature of the bounce or failure. On-Premise systems also allow these codes to be customized, as described in our article Modifying, Adding or Customizing Failure Codes.
The message was rejected by recipient’s mail server.
- 1002-1003 Your message was rejected because it was associated with a blacklist
- 1004 Your message was rejected due to its content
- 1006 Too many connections in a period of time
- 1007 A virus was detected in your message
- 1011 Challenge responses requests
- 1999 Your message was rejected for a reason not specified above
A recipient’s address was found to be invalid.
- 2001 The email address is invalid
- 2002 The domain of the email address is invalid
- 2003 The email address is not in a valid format
- 2004 The email address is no longer valid
- 2999 The email address was rejected for a reason not specified above
Delivery to the recipient’s address is temporarily unavailable.
- 3001 The recipient's mailbox is full or over quota
- 3002 Recipient email account is inactive/disabled
- 3003 Recipient’s server continuously asked us to “try later”
- 3999 The email address was rejected for a reason not specified above
System, network or protocol errors preventing delivery.
- 4001 Recipient’s server too busy
- 4002 Protocol error, invalid command or timeout
- 4003 Unable to connect to recipient's mail server
- 4004 Recipient’s server rejected message as too old
- 4006 Your message was rejected because the receiving server is not accepting mail for the destination domain
- 4999 A system, network or protocol error prevented the delivery of your message for a reason not specified above
Not errors, necessarily, but automated responses designed to provide information
- 5001 Out of office / Auto-reply
- 5999 An informational message was received other than for a reason specified above
Indicates that no other failure codes were encountered.
- 9999 The reason for the failure is unknown.
Updated 10 months ago