ummm... you are referring to the address that the email reply to address is set to?
This is not a program to spoof anything, that would be someone types in that address in the client.

The reply to or from address of any email cannot be trusted ever.

Go in to your mail client, and change the address to trump@whitehouse.gov. Nothing will stop you. People dont need to change their email address... that would not fix anything anyway.