/usr/lib/ghc-doc/hoogle/SMTPClient.txt is in libghc-smtpclient-doc 1.0.4-6build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-smtpclient-doc/html/SMTPClient.txt