Help prevent sending emails to addresses that are known to generate bounces by monitoring and filtering them out while sending emails.

Email bounce

An email bounce signifies the non-delivery of your email message according to RFC3464. When an email gets bounced, the sender receives a delivery status email with the reason for the bounce and the associated status code. For more information about these status codes, see Status codes.

An email address is blocked after it reaches a certain threshold of bounced emails. The default count for blocking the bounced email addresses is 10.

To view the bounce email addresses, navigate to All > System Logs > Bounce Email Addresses.

Important: Disabling bounce management is not recommended as it may lead to slow delivery or blocking of emails by email provider.

Status code

The syntax of the status codes is defined as the following: 
status-code = class "." subject "." detail

      class = "2"/"4"/"5"

      subject = 1*3digit

      detail = 1*3digit

The first subcode indicates whether the delivery attempt was successful. The second subcode indicates the probable source of any delivery anomalies. The third subcode indicates a precise error condition.

Example: Status codes

Table 1. Code 5.1.1
Code Summary Description
5.1.1 Bad destination mailbox address The mailbox specified in the address doesn't exist. For email names, this means the address portion to the left of the "@" sign is invalid.

The default status codes that are used for blocking bounced email addresses are 5.0.*, 5.1.* and 5.7.*, where the asterisks (*) could be any number in the series according to the status code specification.

EExample bounce email address status codes
Note: There is a possibility that some email providers may use non-standard RFC status codes, potentially leading to functional email addresses being blocked. Administrators action is required to unblock these status codes and email addresses.

To view the blocked status codes go to All > System Mailboxes > Administration > Bounce Email Address Status.