Rabbi Dovid Feinstein says don't send meshaloch manot to non-Orthodox Jews, because it is helping sinners.
Why sinners?
Because non-Orthodox Jews won't make the proper blessings before and after eating, Rabbi Feinstein said.
But according to Rabbi Feinstein, if the person is becoming a ba'al teshuva it's okay to send them meshaloch manot food, because the recipient is making progress toward becoming fully Orthodox and it's important to encourage that.
Here's the story in Hebrew on Mako.co.il.