Liquid fuel never leaks out the tailpipe when the engine is running. Excess fuel would be burned up in the catylitic converter.
It is normal for water vapor to come out the pipe looking like 'smoke' upon initial start up. Also, if the exhaust is cool, the vapor condenses and drips out the pipe.
If it's doing this very badly, engine coolant may be getting in the xhaust through a cracked head or blown head gasket.