Email address validation is hard

Email address validation is a pet peeve of mine. So much that I’ve built my own library that I can throw into our projects and be done with it.

So you can imagine my disappoint when an error rolled into our exception tracking system the other day (Actual email address changed to protect the innocent):

Mail::Field::ParseError: Mail::AddressList can not parse |über@example.org|
Reason was: Only able to parse up to ü

At first glance it seemed like we’ve allowed an email address to enter our system, that was so invalidly formatted that the excellent Mail gem couldn’t parse it, causing the application to crash instead of sending a friendly “Welcome” email to the new user. And the culprit was a single ü character.