Message Center: Bounced Messages

Document created by user.m8lcBwVNwY Employee on Nov 19, 2018Last modified by user.oxriBaJeN4 on May 2, 2019
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Bounced MessagesBounced Messages sits within the Message Center and allows administrators to view messages that have been accepted by the Mimecast Gateway but couldn’t be delivered to their recipients.


Messages are bounced for a number of reasons and when this occurs, we send a Non-Delivery Report (NDR) to the message's originator informing them that the delivery failed. To troubleshoot failed delivery, administrators can view information about the message and the reason for the bounce, and use this to address the cause and resend the message.

Bounced messages (both inbound and outbound) are still available in the archive, as the message was originally accepted by Mimecast before being bounced.

Viewing Bounced Messages


To view bounced messages:

  1. Log on to the Administration Console.
  2. Select the Administration toolbar menu item.
  3. Select the Message Center | Bounced Messages menu item.
  4. The information displayed is outlined below. By default, the queue displays all bounces for the day, although bounce information is retained for 30 days. 

    From (Header)The sender's Header From email address. This is used by the email client to display information in the From field.
    From (Envelope)The sender's Envelope From email address. This is used by the SMTP server to generate the NDR.
    ToThe recipient's email address.
    SubjectThe message's subject.
    Date / TimeThe date and time the message was sent.
    IP Address         

    Displays the IP address of the server that bounced the message. If a message is expired from the held queue, no IP will be available.

    This is unlike Message Tracking / Accepted Messages where we display the sending server IP address. 

    Displays whether the message has an attachment or not.

    SizeThe size of the message in KB.
    RouteDisplays whether the message was sent inbound or outbound.
    Bounce InfoDisplays additional information (e.g. a rejection code received by us when attempting delivery, or a reason for the delivery expiring in the delivery queue).
    Bounce Type

    Displays whether the message was a hard or soft bounce:

    • Hard Bounce: The receiving mail server has rejected the connection. Examples of this are an invalid recipient email address, or the mailbox being full.
    • Soft Bounce: The message could not be delivered within our retry schedule (30 attempts over four days). Examples of this are if the recipient's mail server is temporarily unavailable, or the recipient domain's MX records cannot be located.
  5. Select a Bounced Item to view additional information in the Message Details panel. View the Message Center: Managing Message Details page to find out more.
Messages that have been blocked by end users The Digest Email are also logged in bounced messages. These messages are both bounced and the sender’s details added to the user's personal block list.

Customizing the Views


You can optionally customize the view of the bounced messages listing page and apply filters to display only the details that are most relevant. View the Message Center: Customizing Message Views page for further information.


Searching for Bounced Messages


Searching Bounced MessagesTo search for specific bounced messages and refine the results:

  1. Click on the All pull down menu.
  2. Select from one of the following options:
    • From -  Searches by the From email header information.
    • To - Searches by the To email header information.
    • Subject - Searches by the message subject.
    • IP Address - Searches by the IP address of the server that bounced the message.
  3. Enter any known message details in the Search field.
  4. Click on the Search Icon button.


Exporting Search Results


You can export your bounced message search results to a downloadable file. View the Message Center: Exporting Messages page for details.


Mimecast Bounce Information


The most common types of bounces related to Mimecast users are listed below, as displayed under the Bounce Info column. Bounces from remote servers may issue a different reason.


Bounce TypeDescription
Expired in Queue - Rejected by HousekeepingA held item expires from the hold queue.
SMTP Code [Error Description]See the Mimecast SMTP Error Codes page for a full description.
Rejected by Reviewer or an AdministratorAn administrator rejected the message from the hold queue.
Message Bounced - Spam Signature PolicyWe accepted the message but bounced it after a Spam Scanning Policy triggered a reject action.
Message Deleted Due to Content Examination PolicyWe accepted the message but bounced it after a Content Examination Policy triggered a delete action.
Message Deleted Due to Impersonation Protect PolicyWe accepted the message but bounced it after an Impersonation Protection Policy triggered a delete action.
Recipient Email Address is Possibly IncorrectThe recipient's email address doesn't exist.
Recipient Server UnavailableThe destination server couldn't 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 is configured for a delivery IP address and cannot be verified.
Unable to Deliver Encrypted MessageTLS delivery is 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, our connection to the recipient server was rejected.
Connection Timed OutWe were 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.
No Route to HostThe next hop mail server couldn't be contacted, despite a successful connection to the IP address.
Read Timed OutWe were 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 ProtocolWe established the SMTP communication string, and progressed to the MAIL FROM and RCPT TO, but not as far as the DATA command. It's possible that the destination mail server is running low on resources (e.g. memory, available disk space).


Reporting Messages


You can report messages in either the bounced messages listing, or from the message details pop out panel.


Report SpamTo report a message from the bounced messages listing:

  1. Click on the Menu icon icon in the far right corner of the message.
  2. Select to report as:
    • Spam
    • Malware
    • Phishing
  3. Enter your comment / reason into the popup box displayed.
  4. Click on the Report button. The message is submitted to Mimecast for analysis.


To report a message as spam, malware, or phishing from the message details pop out panel:

  1. Click on the Report button.
  2. Selecting the appropriate option.


See Also...