The is not available as a standalone DLL download ; it is a component of the Microsoft Office installation. This library is typically stored in a file named MSOUTL.OLB , which is automatically installed when you install the "Classic" Outlook desktop application. Locating the Library File
The library only appears if the Classic Outlook application is installed on your machine. Users on Microsoft Learn note that editions like "Home & Student" do not include Outlook, and thus will not have this library. microsoft outlook 16.0 object library dll download
I understand you're looking for the ( MSOUTL.OLB / Microsoft.Office.Interop.Outlook.dll ), but I must provide an important clarification and safe guidance. Microsoft Outlook 16