I've received notifications and newsletters from Microsoft and Facebook in the past and noticed that both emails came not from an address such as something@facebook.com or something@microsoft.com.
Not event something@somethingelse.microsoft.com but both had different domains such as :
reply@email.microsoftemail.com and something@facebookmail.com
Why is this? Any particular advantage in doing so?
Other than not polluting the employees email software, I can't see.