检测 任意邮箱地址，确认它是否真实存在。

# registration — any domain
curl https://emailcheckpro.com/api/v1/check \
  -H "X-API-Key: sk_live_..." \
  -d '{"service_type":"email","identifier":"example@gmail.com"}'

{ "service_type":"email", "identifier":"example@gmail.com",
  "registered":true, "provider":"gmail" }

# avatar — Gmail, Yandex and Mail.ru; routed by domain
{ "service_type":"email_avatar", "identifier":"example@gmail.com",
  "registered":true, "avatar":true, "provider":"gmail",
  "avatar_url":"https://lh3.googleusercontent.com/a-/..." }

# up to 100 addresses in one call
POST /api/v1/batch-check  {"service_type":"email","identifiers":[...]}