curl --request GET \
  --url https://api-v2.missioninbox.com/api/email-usage/status/ \
  --header 'Authorization: Basic <encoded-value>'

{
  "user_id": 123,
  "email_usage": 123,
  "metered_credits": 123,
  "user_type": "<string>",
  "email_billing_enabled": true,
  "last_updated": "<string>"
}