The ornamental designs for a mailbox, as shown and described.
FIG. 1 is a front perspective view of a mailbox, with a portion on an outboard motor shown in dashed lines and which portion of an outboard motor does not form a part of the claimed design;
FIG. 2 is a rear view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design;
FIG. 3 is a front view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design;
FIG. 4 is a right side view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design;
FIG. 5 is a left side view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design;
FIG. 6 is a top plan view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design;
FIG. 7 is a bottom plan view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design; and,
FIG. 8 is a front perspective view of the mailbox, with a portion of the outboard motor shown in dashed lines and which portion of the outboard motor does not form a part of the claimed design and the flag shown in an alternate position.
The drawing disclosure of this application includes broken line depictions of an outboard motor of a mailbox, which outboard motor does not form a part of the claimed design.