Which website helps determine the email origin by matching domain names with IP addresses?

The website arin.net is indeed the correct answer as it serves a significant role in helping users determine the origin of email by matching domain names with IP addresses. ARIN, or the American Registry for Internet Numbers, provides a database where users can look up information related to IP addresses, Autonomous System Numbers (ASNs), and associated organizations. By performing a WHOIS lookup on a specific IP address through ARIN, one can trace it back to the registered domain name and its owning entity, therefore establishing the email's origin.

The other websites mentioned serve different roles. For instance, toolbar.netcraft.com is primarily known for providing information about the technologies that a website is using, rather than specifically focusing on email origin checks. Hg.org serves as a legal resource and doesn't provide the needed lookup services related to IPs and domains. Phishtank.com is focused on identifying and reporting phishing efforts; while it can help in identifying unsafe domains, it does not function as a tool for tracing email origins through IP matching.