Bounced Messages

Document created by user.oxriBaJeN4 Employee on Sep 11, 2015Last modified by user.oxriBaJeN4 Employee on Mar 25, 2018
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Bounced messages that we've accepted, but cannot deliver to the next hop or mail server. Messages are bounced for a number of reasons (mentioned below) but when this occurs a notification is sent to the message's sender. Administrators can view information on bounced messages in the bounce viewer, including the reason for the bounce. You can use this to address the cause, and resend the message.


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 us when attempting delivery, or a reason for the delivery expiring in the delivery queue).


Searching for a Bounced Message


To search for a bounced email:

  1. Log on to the Administration Console.
  2. Select the Administration toolbar menu item.
  3. Select the Monitoring | Bounces menu item.
  4. Enter an Email Address or Domain Name in the search bar.
  5. Select the Search button. The results are displayed.
  6. Select a Bounced Item to view the bounce properties.

In the example shown, the recipients mail server rejected / bounced the message when we attempted delivery. If a message we attempt to deliver is bounced, we send a Non-Delivery Report (NDR) to the message's originator informing them that the delivery failed.


There are two types of bounces, represented by colored icons in the bounce viewer.


Icon ColorBounce TypeDescription
RedHard BounceThe receiving mail server has rejected the connection. Examples of this are an invalid recipient email address, or the mailbox being full.
OrangeSoft BounceThe 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.


Messages that have been blocked by end users The Digest Email are also logged in the bounce viewer. These messages are both bounced and the sender’s details added to the user's personal block list.

Bounced messages (both outbound and inbound) are still available in the 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. Select the Export Data button.
  2. Specify an export file location.


Bounce Reasons


The most common types of bounce descriptions are:


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 Bounced Due to Content Examination PolicyWe accepted the message, but bounced it after a Content Examination Policy triggered a bounce action.
Message Deleted Due to Content Examination PolicyWe accepted the message, but bounced it after a Content Examination 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 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 is possible that the destination mail server is running low on resources (e.g. memory, available disk space).
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