A weatherproof back box for receiving a fire alarm notification or other fire alarm device includes a back wall and sidewalls that project from the back wall and define a mouth. The sidewalls further include recessed portions that extend from the back wall toward the mouth, and end prior to the mouth. The back box further includes mounting posts, which are preferably less than 50% of the depth of the back box, that project from the recessed portions into the mouth. Additionally, these mounting posts receive fasteners for securing the fire alarm notification device in the mouth of the back box.