((a)) ** .—** This subchapter shall apply with respect to—
((1)) first-class mail letters and sealed parcels;
((2)) first-class mail cards;
((3)) periodicals;
((4)) standard mail;
((5)) single-piece parcel post;
((6)) media mail;
((7)) bound printed matter;
((8)) library mail;
((9)) special services; and
((10)) single-piece international mail,
((b)) ** .—** Mail matter referred to in subsection (a) shall, for purposes of this subchapter, be considered to have the meaning given to such mail matter under the mail classification schedule.