Netmail Archive 6.x
In order to perform operations with PST files (eg. import/export) the Archive servers will require Microsoft Outlook installed on them. Supported versions include Outlook 2010/2013/2016, and it must be 32-bit. However attempting to install the software on the Archive server may result in a message similar to "Outlook is already installed on this computer".
The cause of this error is often due to the presence of Messaging API & Collaboration Data Objects. Find this item in the Control Panel -> Programs & Features, uninstall it, and try the Outlook deployment again.
Messaging API & Collaboration Data Objects is delivered by default on the Archive servers because it is required to process signed/encrypted messages using the Redemption API. Outlook also provides this functionality however Netmail does not have rights to distribute this software.