A Program is trying to Send an email on your Behalf 

For this, the following options should then be set:

• Configure Outlook to use Group Policy Security settings
  Administrative Templates-> Microsoft Outlook <version>-> Security-> Security Form Settings-> option: Outlook Security mode-> setting: Use Outlook Security Group Policy
• Set the Guard Behavior to Automatically Approve for each prompt
  Administrative Templates-> Microsoft Outlook <version>-> Security-> Security Form Settings-> Programmatic Security

This results in the following Registry keys being set:

Key: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\<version>\Outlook\Security
Value name: AdminSecurityMode
Value type: REG_DWORD
Value: 3

Key: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\<version>\Outlook\Security
Value name: PromptOOMSend
Value name: PromptOOMAddressBookAccess
Value name: PromptOOMAddressInformationAccess
Value name: PromptOOMMeetingTaskRequestResponse
Value name: PromptOOMSaveAs
Value name: PromptOOMFormulaAccess
Value name: PromptSimpleMAPISend
Value name: PromptSimpleMAPINameResolve
Value name: PromptSimpleMAPIOpenMessage
Value type: REG_DWORD
Value: 2

disableprogrammaticsecurity.zip

https://www.msoutlook.info/question/883

Outlook Version Reference