Mailhouse is a graduate of Suffield Academy. In the early 1990s, he appeared on the soap opera Days of Our Lives. He appeared in guest roles in a variety of television series in the 1990s, including Seinfeld, Picket Fences, Melrose Place, Caroline in the City (1997), Dharma & Greg (1999) and Sports Night (1998-2000), in a recurring role as CSC executive JJ. In the 2000s, he appeared in episodes of television series such as Judging Amy (2002) and C.S.I.: Crime Scene Investigation (2003). He has also appeared in several films, including Speed (1994). As a musician, he played drums with the grunge-alternative rock band Dogstar, which has opened for David Bowie and toured with Bon Jovi. The band released an EP entitled Quattro Formagi (1995) and two albums: Our Little Visionary (Zoo/BMG, 1996) and Happy Ending (2000). Dogstar attracted media attention from the off-stage job held by its bassist Keanu Reeves as a Hollywood actor. In 2011, Mailhouse starred in A Christmas Pageant with actress, Melissa Gilbert.
