Почему POP3 не работает, когда IMAP работает в Thunderbird?

Существует аналогичная разница между двумя инструментами для пакетов .deb.

Похоже, что файл использует /etc/mime.types, а mimetype использует намного сложную заготовку большего количества XDG_DATA_DIRS (из [ f6]):

ENVIRONMENT
       XDG_DATA_HOME
       XDG_DATA_DIRS
           These variables can list base directories to search for data files. The shared mime-info will be expected in the "mime" sub directory of one of these directories. If these are not set,
           there will be searched for the following directories:

                   $HOME/.local/share/mime
                   /usr/local/share/mime
                   /usr/share/mime

           See also the "XDG Base Directory Specification" http://freedesktop.org/Standards/basedir-spec <http://freedesktop.org/Standards/basedir-spec>

FILES
       The base dir for all data files is determined by two environment variables, see "ENVIRONMENT".

       BASE/mime/packages/SOURCE.xml
           All other files are compiled from these source files. To re-compile them use update-mime-database(1).

       BASE/mime/globs
           Compiled information about globs.

       BASE/mime/magic
           Compiled information about magic numbers.

       BASE/mime/MEDIA/SUBTYPE.xml
           Descriptions of a mimetype in multiple languages, used for the "--describe" switch.