The ornamental design for a outerbox of a mouse trap, as shown and described.
FIG. 1 is an upper perspective view of an outer box of a mouse trap showing my new design.
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is an opposite side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view; and,
FIG. 8 is an exploded perspective view of the outer box of a mouse trap.
The features presented in broken lines in FIG. 8 represent unclaimed inner components of the outer box of a mouse trap and form no part of the claimed design.