/usr/include/KF5/KTNEF/ is in libkf5tnef-dev 4:15.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/KTNEF/KTNEF/
/usr/include/KF5/KTNEF/KTNEF/Formatter
/usr/include/KF5/KTNEF/KTNEF/KTNEFAttach
/usr/include/KF5/KTNEF/KTNEF/KTNEFDefs
/usr/include/KF5/KTNEF/KTNEF/KTNEFMessage
/usr/include/KF5/KTNEF/KTNEF/KTNEFParser
/usr/include/KF5/KTNEF/KTNEF/KTNEFProperty
/usr/include/KF5/KTNEF/KTNEF/KTNEFPropertySet
/usr/include/KF5/KTNEF/KTNEF/KTNEFWriter
/usr/include/KF5/KTNEF/ktnef/
/usr/include/KF5/KTNEF/ktnef/formatter.h
/usr/include/KF5/KTNEF/ktnef/ktnef_export.h
/usr/include/KF5/KTNEF/ktnef/ktnefattach.h
/usr/include/KF5/KTNEF/ktnef/ktnefdefs.h
/usr/include/KF5/KTNEF/ktnef/ktnefmessage.h
/usr/include/KF5/KTNEF/ktnef/ktnefparser.h
/usr/include/KF5/KTNEF/ktnef/ktnefproperty.h
/usr/include/KF5/KTNEF/ktnef/ktnefpropertyset.h
/usr/include/KF5/KTNEF/ktnef/ktnefwriter.h