Just close enough. It´s bluetooth.
If your remote is an RF remote, then it should work fine as long as the closet doors/walls don't end up blocking the signal.
There is a finite distance limit for an RF remote and things like doors and/or walls can/will reduce the range.
The only way to know for sure would be to test/try it, and if you have any problems, try changing the position/location of the MiBox within the closet to see if you can find one that will allow it to work.
I hope this made sense and was helpful.
Best wishes and good luck!
Yes, it will work properly because it uses a bluetooth connection.