the 500-mile email

networkingops culture

A classic sysadmin tale of an email system that mysteriously could not send mail farther than about 500 miles.

Trey Harris's story turns out to have a real cause: a broken config defaulted a network timeout to near zero, so only servers close enough to answer within a few milliseconds ever connected, and a few milliseconds of light-speed round trip works out to roughly 500 miles. It is the perfect parable for why the absurd-sounding symptom deserves a real root-cause hunt.

Also known as: 500 mile email, 500-mile email, Trey Harris

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