When we traveled fulltime in our RV, we used My RV Mail Service located in Crestview, Florida. We used their address as our domicile and received great service from them. They are very reasonable and offer a variety of services. The mail appears in your inbox, you choose to forward it or shred it by a click of a button. Here is their website...
Best US Mail Forwarding Service for RVers/Travelers | Physical Street Addresses for Businesses - MyRVmail