I just want to save this information from comments. [@ilian](https://mathematica.stackexchange.com/users/145/ilian) mentioned [in comments](https://mathematica.stackexchange.com/questions/174474/catching-machineunderflow-in-version-11-3#comment458076_174474): 

>This command is simply not needed in 11.3 and later because what it accomplishes is now the default (and only) behavior, so you can think of `CatchMachineUnderflow` as being permanently set to `False`. There are also some new warning messages that can be easily turned off.