ContributionsMost RecentMost LikesSolutionsIntegration with Outlook Failing - System.InvalidCastException Please help. When I go to send POs out of Myob, it crashes and cannot send an email so I have to download and attached to an email. Error code: System.InvalidCastException Message: Unable to cast COM object of type 'Microsoft.Office.Interop.Outlook.ApplicationClass' to interface type 'Microsoft.Office.Interop.Outlook._Application'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{00063001-0000-0000-C000-000000000046}' failed due to the following error: Interface not registered (Exception from HRESULT: 0x80040155). Solved