Go to searchcarrier.com, punch in random DOTs from those PO-box listings — watch the red flags explode: suspended authority, no safety rating, fake addresses, revoked insurance, carriers that "disappeared" after one load.
Fuck every single one of these shady broker cunts, fake carrier scumbags, DOT-number-flipping fraudsters, and the FMCSA limp-dicked bureaucrats who let this shit slide for years.