/usr/include/KF5/Akonadi/KMime/ is in libkf5akonadimime-dev 4:17.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/Akonadi/KMime/AddressAttribute
/usr/include/KF5/Akonadi/KMime/CommandBase
/usr/include/KF5/Akonadi/KMime/MarkAsCommand
/usr/include/KF5/Akonadi/KMime/MessageFlags
/usr/include/KF5/Akonadi/KMime/MessageFolderAttribute
/usr/include/KF5/Akonadi/KMime/MessageModel
/usr/include/KF5/Akonadi/KMime/MessageParts
/usr/include/KF5/Akonadi/KMime/MessageStatus
/usr/include/KF5/Akonadi/KMime/MoveCommand
/usr/include/KF5/Akonadi/KMime/RemoveDuplicatesJob
/usr/include/KF5/Akonadi/KMime/SpecialMailCollections
/usr/include/KF5/Akonadi/KMime/SpecialMailCollectionsDiscoveryJob
/usr/include/KF5/Akonadi/KMime/SpecialMailCollectionsRequestJob
/usr/include/KF5/Akonadi/KMime/StandardMailActionManager