/usr/lib/x86_64-linux-gnu/libsylpheed-plugin-0.so is in sylpheed 3.4.0~beta7-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libsylpheed-plugin-0.so.1.1.0
/usr/lib/x86_64-linux-gnu/libsylpheed-plugin-0.so.1.1.0