https://docs.istmp.email/intro-2052467m0 https://docs.istmp.email/check-an-email-address-31502341e0 https://docs.istmp.email/checkresult-13754189d0 https://docs.istmp.email/signals-13754190d0 https://docs.istmp.email/errorresponse-13754191d0 https://docs.istmp.email/ratelimiterror-13754192d0 https://docs.istmp.email/validationerrorresponse-13754193d0