curl --request POST \
  --url https://api.thanks.io/api/v2/send/letter \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "front_image_url": "https://s3.amazonaws.com/cdn.thanks.io/user_image_library/gFBaJJJWRp60op3ZOoK7UaO5I7zi33rdKQGgHylR.png",
  "message": "Hey %FIRST_NAME%!,\n\nTHANK YOU for allowing us the opportunity to HELP you with your plan!",
  "recipients": [
    {
      "name": "Current Resident",
      "address": "123 Main Street",
      "city": "Fake City",
      "province": "NY",
      "postal_code": "55555",
      "country": "US",
      "custom1": "Example Custom 1",
      "custom2": "Example Custom 2",
      "custom3": "Example Custom 3",
      "custom4": "Example Custom 4"
    },
    {
      "name": "Jane Doe",
      "address": "456 Another St",
      "city": "Fake City",
      "province": "NY",
      "postal_code": "55555",
      "country": "US"
    }
  ]
}'

{
  "total_estimated_recipients": 1,
  "authorization_total": 60,
  "leads_fee": 0,
  "mailing_list_ids_used": "",
  "additional_letter_pages_count": 0,
  "handwriting_color": "rgba(31,0,113,0.80)",
  "front_image": "https://s3.amazonaws.com/cdn.thanks.io/user_image_library/gFBaJJJWRp60op3ZOoK7UaO5I7zi33rdKQGgHylR.png",
  "message": "Test Message",
  "append_or_current_resident": true,
  "type": "letter",
  "return_name": "Custom Return",
  "return_address": "1 Main Street",
  "return_address2": "Unit 1",
  "return_city": "Woodbridge",
  "return_province": "NJ",
  "return_postal_code": "07095",
  "message_template_id": null,
  "image_template_id": null,
  "method": "api",
  "sub_account_id": null,
  "font_size": "auto",
  "qrcode_url": null,
  "custom_background_url": null,
  "giftcard_brand": null,
  "giftcard_image": null,
  "giftcard_amount": null,
  "status": "reviewing",
  "addons": {
    "standardmail": "on"
  },
  "style": 5,
  "user_id": 2,
  "updated_at": "2025-08-15 03:22:20",
  "created_at": "2025-08-15 03:22:19",
  "id": 42670,
  "display_status": "Reviewing",
  "display_trigger": "API",
  "display_type": "Windowed Letter",
  "giftcard_brand_longname": "",
  "sub_account": null,
  "recipients": [
    {
      "name": "Current Resident",
      "address": "1 Main Street",
      "city": "Anytown",
      "province": "NY",
      "postal_code": "55555",
      "country": "US",
      "address2": ""
    }
  ]
}