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Exchange Stubbing

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This article refers to the Barracuda Message Archiver firmware version 5.2 or higher, Barracuda Archive Search for Outlook version 5.2 or higher, and Microsoft Exchange Server 2007, 2010, 2013, 2016, and 2019.

Verify Barracuda Archive Search for Outlook version (available for download on the USERS > Client Downloads page in the Barracuda Message Archiver web interface) is the same major revision as the Barracuda Message Archiver firmware for proper functionality.

For stubbing and Microsoft Exchange imports initiated via the Barracuda Message Archiver user interface, there is a 100MB limit on file import.

Whitespace Recovery

Once stubbing is complete, view the Microsoft technet article Eseutil /D Defragmentation Mode to determine how best to recover whitespace located within the Exchange Server mailstore.

You can enable stubbing to store attachments on the Barracuda Message Archiver rather than on the Microsoft Exchange servers to reduce storage capacity on the servers, in some cases by as much as 70%. Exchange Stubbing configuration is done on the MAIL SOURCES > Exchange Integration page. For detailed information, click Help in the web interface.

To require users to log into the Barracuda Message Archiver web interface to open an attachment from a stubbed message, go to the USERS > Client Downloads page. In the Client Access section, set Require Login to View Mail to Yes. Click Save at the top of the page to save your setting.

During the stubbing process, the Barracuda Message Archiver adds all attachments (Attachments Only option), or the entire message (Entire Message option) for a message to its own storage database and creates a hyperlink, or stub, to the original attachment or message depending on the option you select in the Exchange Integration page. The attachment from the original message, or if selected, the entire message, is then removed from your Exchange server and replaced with the stubs so that any requests to access the file or message is automatically redirected to, and served from, the Barracuda Message Archiver. A short message containing the names and sizes of the stubbed content is placed in every "stubbed" email, along with a hyperlink where users can easily access the attachments regardless of what email client is used, including Outlook Web Access.

To open a stubbed link in Outlook, click on the stub and enter your Barracuda Message Archiver login credentials. The attachment is automatically downloaded to your local system. Note that you are not redirected to the Barracuda Message Archiver web interface.

  • Attachments Only – When selected, the attachment is removed from the message and the attachment is replaced with an attachment indicator and a link to the preserved attachment:

If there are no attachments in the message, then nothing is stubbed and the entire message is left intact.

  • Entire Message – When selected, the entire message body is replaced with a text excerpt containing a link to the original message:

View stubbed emails using the Barracuda Message Archiver Outlook Add-in. When a stubbed email is accessed through Archive Search for Outlook, the attachment is automatically downloaded and displayed as part of the original email. The attachment is readily available for viewing or dragging onto the desktop, making the stubbing process virtually invisible.


In order for remote users of Archive Search for Outlook to interact with the Barracuda Message Archiver, the Web Interface Ports specified on the BASIC > Administration page and on the ADVANCED > Secure Administration page must be configured on your corporate firewall to accept incoming connections.


The stubbing process can be initiated on demand or configured to run nightly. All messages that are currently on your Exchange Server that meet the provided criteria are stubbed. When configured to run nightly, the process starts at 10PM when the additional system load on the Barracuda Message Archiver least impacts users.

Policy-Based Stubbing

The Barracuda Message Archiver only stubs messages that meet your specified criteria, which can be any combination of the following:

  • Mailbox – Messages in the specified accounts
  • Age – Messages older than the specified number of days
    Size – Messages larger than the specified size. Minimum size allowed is 10KB

You can configure multiple stubbing policies, including all stubbing procedures and their results and statuses, listed on the MAIL SOURCES > Exchange Integration  page in the Recent Actions section.

End-User Controls

Archive Search for Outlook retrieves the attachment and places it inline to ensure that email messages and attachments appear as they would prior to Exchange stubbing. Archive Search for Outlook can also be used to temporarily unstub and re-stub specific messages. Any message unstubbed in this manner remains so for 30 days, after which time it is re-stubbed during the next automatic stubbing process.


Barracuda Networks strongly recommends unstubbing your data before you mirror it to the cloud. Contact Barracuda Networks Technical Support  for more information.

Unstubbing a message causes the Barracuda Message Archiver to place the attachment back into the body of the message. To restore stubbed content to your Microsoft Exchange Server, click the  Restore  ( restore_icon5x.png ) icon in the Outlook toolbar. This is most useful when individual end users are on the road and need immediate access to all attachments in a message even while not directly connected to the mail server. Any message that is unstubbed by the user remains so until it is re-stubbed by that user, or after 30 days; it is not re-stubbed by either an immediate or nightly stubbing process during this time.