‘Set-ItemProperty Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice   -name ProgId Outlook.URL.mailto.14’

&

‘Set-ItemProperty Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice   -name ProgId Outlook.URL.mailto.15’

OR

‘Set-ItemProperty  HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice\\Progid  = Outlook.URL.mailto.14’

&

‘Set-ItemProperty  HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice\\Progid  = Outlook.URL.mailto.15’

and for PDF datatype extension i will do the following:
                                                                                                                                                                                                                          ‘Set-ItemProperty Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice   -name ProgId PDFXEdit.PDF’

‘Set-ItemProperty  HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations\mailto\UserChoice\\Progid  = PDFXEdit.PDF’