curl https://api.v2.dealmachine.com/v1/mail/return-addresses \
  -H "Authorization: Bearer dm_sk_live_xxx"

{
  "data": [
    {
      "id": "42",
      "label": "Office",
      "name": "Acme Real Estate",
      "address_1": "456 Business Ave",
      "address_2": "Suite 200",
      "city": "Austin",
      "state": "TX",
      "zip": "78702",
      "is_validated": true,
      "is_default": true,
      "created_at": "2026-01-15T10:00:00Z",
      "updated_at": "2026-01-15T10:00:00Z"
    }
  ]
}