Bounced Messages

Document created by user.oxriBaJeN4 Employee on Sep 11, 2015Last modified by user.oxriBaJeN4 Employee on Dec 18, 2017
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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:

  1. Log on to the Administration Console.
  2. Click on the Administration toolbar button. A menu drop down is displayed.
  3. 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:

  1. Enter an Email Address or Domain Name in the search bar.
  2. Click the Search button. The results are displayed.
  3. 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 ColorBounce TypeDescription
RedHard BounceIndicates that the receiving mail server has rejected the connection. Some examples of this are an invalid recipient email address, or the mailbox being full.
OrangeSoft BounceIndicates 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:

  1. Click on the Export Data button.
  2. Specify the location of the export file.


Bounce Reasons

The following table outlines the most common types of bounce descriptions:


Bounce TypeDescription
Expired in Queue - Rejected by HousekeepingA 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 AdministratorAn administrator manually rejected the email from the Held queue
Message Bounced - Spam Signature PolicyMimecast accepted the message, then bounced it after a Configuring Spam Scanning Definitions and Policies triggered a reject action.
Message Bounced Due to Content Examination PolicyMimecast accepted the message, then bounced it after a Configuring Content Examination Definitions and Policies triggered a bounce action.
Message Deleted Due to Content Examination PolicyMimecast accepted the message, then bounced it after a Configuring Content Examination Definitions and Policies triggered a delete action.
Recipient Email Address is Possibly IncorrectThe recipient's email address did not exist.
Recipient Server UnavailableThe destination server could not be contacted, although the IP address was resolved.
Recipient Email Server Rejected the MessageThe destination server rejected the message.
Recipient Mailbox is FullThe destination user's mailbox is unable to accept more messages.
Unable to Authenticate During SendSMTP Authentication has been configured for a Delivery IP address and cannot be verified.
Unable to Deliver Encrypted MessageTLS delivery has been enforced, but the remote server doesn't support it.
Unable to Move Email to CCMA CCM item cannot be added to a CCM mailbox.
Connection RefusedOn delivery, Mimecast's connection to the recipient server was rejected.
Connection Timed OutMimecast was unable to connect to the delivery IP address.
Domain has no MX Records or is InvalidThe 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 ListA user rejected the message with an available tool or with a digest.
No Route to HostThe next hop mail server couldn't be contacted, despite successful connection to the IP address.
Read Timed OutMimecast was waiting for a reply during the SMTP transmission, which wasn't received in a timely fashion.
Temporary Error Looking Up MX recordThe DNS or associated MX records for the destination domain couldn't be resolved.
Could Not Progress Past Recipient in ProtocolMimecast 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).
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