tech
January 27, 2026
Why has Microsoft been routing example.com traffic to a company in Japan?
Company’s autodiscover caused users’ test credentials to be sent outside Microsoft networks.
TL;DR
- Microsoft's autodiscover service incorrectly routed traffic for example.com to sei.co.jp, a Japanese company.
- example.com is reserved for testing purposes under RFC2606 and should not be routable.
- The misconfiguration could have exposed test credentials when users set up Outlook accounts with example.com domains.
- Microsoft has updated the service to stop the improper routing and is investigating the cause.
- The incident brings to light potential vulnerabilities on Microsoft's network, drawing parallels to a past security breach involving a mishandled test account.