This error is caused by a particular library not being installed on the workstation that is required to send email. Please follow these steps.
For users with Office/Outlook not installed at all:
Follow this link and download and install the the library.
For users with Outlook 2007 and later:
Follow this link and download and install the library.
For users with Outlook 2003 and earlier:
The library may not have been installed by default when Outlook was installed but it can be added to your installation easily.
-Open Control Panel -> Add/Remove Programs or Programs and Features
-Find and highlight the Outlook/Office install and select to change/modify it. In the wizard select to Add or Remove Features, click Next and make sure the box for choosing Advanced Customization is checked.
-In the screen on the wizard that offers a list of features to add or remove locate the Data Collaboration Objects feature, right click it and select Run All From My Computer.
-Finish the wizard and it should install the missing library.