The state of the email address

Abstract

Electronic mail is an unquestionably vital component of the Internet infrastructure. While the general perception of email is that it "just works," surprisingly little data is available to substantiate this claim. While SMTP is a mature technology of over twenty years, the architecture is increasingly strained by both normal and unsolicited load. In this paper we seek to provide a greater understanding of the behavior of Internet email as a system using active measurement.In order to survey a significant, diverse, and representative set of Internet SMTP servers, to which we have no administrative access, we develop a testing methodology that provides an email "traceroute" mechanism. Using this mechanism, we measure email loss, latency, and errors over the course of a month to popular, random, and Fortune 500 domains. Our initial results are quite unexpected and include non-trivial loss rates, latencies longer than days, and significant and surprising errors. While we present plausible explanations for some of these phenomena, there are several that we cannot, as of yet, explain. By better understanding Internet protocols which lack explicit end-to-end connection semantics, our eventual hope is to derive guidelines for designing future networks and more reliable email systems.