Bounced messages are those that Mimecast has accepted, but cannot deliver to the next hop or mail server. When this happens, a notification is sent to the sender of the message. Messages may be bounced due to a number of possible reasons (mentioned below). Administrators can view information on messages that Mimecast was unable to deliver via the Bounce Viewer. It provides information on messages, including the reason for the bounce. Administrator can use this to address the cause and resend the message.
Accessing the Bounce Viewer
To access the bounce viewer:
- Log in to the Administration Console.
- Click on the Administration toolbar button. A menu drop down is displayed.
- Click on the Monitoring | Bounces menu item.
By default the bounce viewer displays all bounces for the day, although bounce information is retained for 30 days. The information provided includes the:
- Sender's address
- Recipient’s address
- Message subject
- Message size
- Send date and time
- Additional information (e.g. a rejection code received by Mimecast when attempting delivery, or a reason for the delivery expiring in the delivery queue).
Searching for a Bounced Message
To search for a specific bounced email:
- Enter an Email Address or Domain Name in the search bar.
- Click the Search button. The results are displayed.
- Click on a Bounced Item to view the bounce properties.
In the example above, the recipients mail server rejected / bounced the message when Mimecast attempted delivery. This allows the administrator to establish why delivery failed and resolve the issue. If a message that Mimecast attempts to deliver is bounced, Mimecast generates a bounce message or Non-Delivery Report (NDR). This is sent to the original sender of the email informing them that the delivery failed .
There are two types of bounces, represented by different colored icons in the bounce viewer.
|Icon Color||Bounce Type||Description|
|Red||Hard Bounce||Indicates that the receiving mail server has rejected the connection. Some examples of this are an invalid recipient email address, or the mailbox being full.|
|Orange||Soft Bounce||Indicates that the message could not be delivered within the Mimecast stipulated retry schedule (30 attempts over 4 days). An example of this would be if the recipient's mail server is temporarily unavailable, or if the MX records for the recipient’s domain cannot be located.|
Messages that have been blocked by end users Using a Digest are also logged in the bounce viewer. Mimecast bounces these emails, as well as adding the sender’s details to their personal block list.
Emails that have been bounced (both outbound and inbound) are still available in the Mimecast archive, as the Message was originally accepted before being bounced.
Exporting a Bounced Search's Results
To export the results of a bounced search:
- Click on the Export Data button.
- Specify the location of the export file.
The following table outlines the most common types of bounce descriptions:
|Expired in Queue - Rejected by Housekeeping||A held item expires from the Held Queue|
|SMTP Code [Error Description]||View the full article for a description of Mimecast SMTP Error Codes|
|Rejected by Reviewer or an Administrator||An administrator manually rejected the email from the Held queue|
|Message Bounced - Spam Signature Policy||Mimecast accepted the message, then bounced it after a Spam Scanning Policies triggered a reject action.|
|Message Bounced Due to Content Examination Policy||Mimecast accepted the message, then bounced it after a Configuring a Content Examination Policy triggered a bounce action.|
|Message Deleted Due to Content Examination Policy||Mimecast accepted the message, then bounced it after a Configuring a Content Examination Policy triggered a delete action.|
|Recipient Email Address is Possibly Incorrect||The recipient's email address did not exist.|
|Recipient Server Unavailable||The destination server could not be contacted, although the IP address was resolved.|
|Recipient Email Server Rejected the Message||The destination server rejected the message.|
|Recipient Mailbox is Full||The destination user's mailbox is unable to accept more messages.|
|Unable to Authenticate During Send||SMTP Authentication has been configured for a Delivery IP address and cannot be verified.|
|Unable to Deliver Encrypted Message||TLS delivery has been enforced, but the remote server doesn't support it.|
|Unable to Move Email to CCM||A CCM item cannot be added to a CCM mailbox.|
|Connection Refused||On delivery, Mimecast's connection to the recipient server was rejected.|
|Connection Timed Out||Mimecast was unable to connect to the delivery IP address.|
|Domain has no MX Records or is Invalid||The DNS lookup is producing empty MX records. This is normally due to a spelling mistake in the email address's domain.|
|Expired in Queue - Rejected by User Header Block List||A user rejected the message with an available tool or with a digest.|
|No Route to Host||The next hop mail server couldn't be contacted, despite successful connection to the IP address.|
|Read Timed Out||Mimecast was waiting for a reply during the SMTP transmission, which wasn't received in a timely fashion.|
|Temporary Error Looking Up MX record||The DNS or associated MX records for the destination domain couldn't be resolved.|
|Could Not Progress Past Recipient in Protocol||Mimecast established the SMTP communication string, and progressed to the MAIL FROM and RCPT TO, but not as far as the DATA command. It is possible that the destination mail server is running low on resources (e.g. memory, available disk space).|