Currently the Device Approval mail which is system generated takes the "From" address as user address. The To address could be either Admins mentioned for approval or user for information. Currently there is no way to customize this "From" address to something like Administrator's address or Generic address.
So there is a feature request to have this feature, so that "From" address will look like how the customer wants it.
This Enhancement Request is submitted for Travelre V11 and V12 products.