Message Attachments

Document created by user.oxriBaJeN4 Employee on Sep 11, 2015Last modified by user.oxriBaJeN4 Employee on Oct 9, 2017
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Any attachment that is blocked or stripped and linked from a message based on an attachment policy, is logged and available for release by an administrator using stripped attachments. Attachment policies are based on mail flow, and can be applied to both inbound or outbound mail. Using a separate view, attachments sent using Mimecast's Large File Send can also be tracked.

If you have the Targeted Threat Protection - Attachment Protect product on your Mimecast account, you can release attachments to the Sandbox. Contact your Account Manager for further details.

There are four policies that can be used to handle attachments. All are located in the Administration | Gateway | Policies section:

Attachment ManagementAllows individual attachment types to be blocked, linked or held using an Attachment Set 
Attachment Block on SizeRemoves attachments based on the cumulative size of the attachments.
Attachment Hold on SizeHolds the email based on the cumulative size of the attachments.
Attachment Link on SizeStrips and Links all attachments based on the cumulative size of the attachments.

It is also possible to limit messages based on the total size of the message, including all attachments. The Policies above will affect individual attachments only.

How do Stripped Attachments work?


When an attachment is blocked or stripped and linked to a message, your internal end users will be notified. Administrators can then review, and if required, release either the attachment (which will be delivered with a system notification) or the original email. This is then delivered to the recipient.


These attachments are available in the Archive until the email's expiry date. For more information on email retention, refer to the Retention Adjustments page. Delivery of and access to Large File Send items can be monitored in a separate viewer.


Viewing Messages with Stripped Attachments


To view attachments that have been removed from messages, log on to the Administration Console, and navigate to Administration | Monitoring | Attachments. The following information regarding the message and the associated attachments is displayed:



The column Ext shows the File extension for the attachment, and refers to the actual MIME type of the attachment. Therefore even if the attachment file type has been renamed, the actual file type will be displayed.


The Status column displays an icon showing the status of the attachment, as detailed below:

IconAttachment StatusDescription
Attachment LinkedThe attachment has been removed from the original email due to a  strip and link policy. This could either be using an Attachment Link on Size policy, or by selecting the link option in an Attachment Set. The end user will receive the original email, with a  system notification attachment. A HTTPS hyperlink is provided for the end user to download the attachment directly from Mimecast.
Attachment_released.gifAttachment ReleasedThe attachment, or the original message with an attachment, has been released by an Administrator to the end user.
Blocked_Attachment.gifAttachment BlockedThis indicates that the attachment has been blocked due to an Attachment Management Policy or Attachment Block on Size Policy.


The search field allows an Administrator to filter the view by searching for the FROM, TO address or filename. By default, Stripped Attachments displays one month's worth of attachments. The date range can also be changed by using the 'From' and 'To' calendar controls, and clicking the reload button.


Additional information is provided when a message is selected, including the message status and the details of the attachment as below:


If the Released field value is set to Yes, the attachment is released by the Administrator. If the value for this field is set to No, the attachment has not yet been released by the Administrator. This field only applies to Attachment Block on Size Policies, or Attachment Management Policies where the Deny option has been enabled.


Releasing Emails and Attachments


To release an attachment:

  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 | Attachments menu item.
  4. Right-click on the message which displays the following options:

  5. Select one of the following options:
    Release Original MessageReleases the original message with attachment to the end user, which maintains the context of the attachment.
    Release AttachmentReleases the attachment via a system notification to the end user.
    View Attachment DetailThis option displays the Stripped Attachment Review page as displayed above.
    View Email DataDisplays the contents of the email for an Administrator, and allows for a preview of the attachment prior to releasing to the end user.

    You can select multiple attachments to be released by using the check box next to each item, and selecting the Release Attachment button on the top toolbar.

Released Attachments Log


When an item is released from Stripped Attachments, an entry is listed in the Released Attachments Log. To view the log:

  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 | Attachments menu item.
  4. From the View drop down, select the Release Log menu option:

  5. The release log is displayed for the last month by default, and provides the following information:



    Released By

    Provides the email address of the user (if released via a Digest) or the Administrator who released the attachment.

    Attachment Name

    The full name of the attachment.
    Released ToThe email address to which the attachment was delivered.
    MethodSpecifies how the attachment was released. This can either be from the Administration Console or Self Release (for an attachment that has been downloaded from the link provided).
    TypeSpecifies whether it was the original email that was released, or only the attachment.
    Date TimeTime and date that the message was released.
    Administrators are also able to customize the Attachment Block and Attachment Release notifications. For more information, refer to the Configuring Notification Sets Definitions and Policies article.


Large File Send Attachments


Large File Send services can be enabled through Mimecast for Outlook and Mimecast for Mac when composing new messages, or by Attachment Management Policies. Large File Send attachments are not transmitted through the company email server, but are instead sent directly through Mimecast. This helps to reduce the load on the server and user application.

Large File Send Attachments can be released from this viewer by those with Content Viewing rights.

Users can monitor the Large File Send files from the Mimecast ribbon in Mimecast for Outlook or from the Large File Send manager in Mimecast for Mac. Administrators can monitor these files from the Administration Console, under the Administration | Monitoring | Attachments menu. Select the Large File Send Attachments button to view a list of the files.






Select one of the files to view more details on the file, including the email receipt/delivery details.

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