Why Email Validation Is Hard by @jshauma
From an article titled “Your E-Mail Validation Logic is Wrong“ dispelling our notions about the ease of email validation.
- Email addresses can contain multiple ‘@’ symbols
- Bang paths – addresses with ‘!’ – may be accepted
- The percent sign may lead to relaying
- Various punctuation characters are allowed.
- Plus signs aren’t special, except when they are
- Dots are special
- Quoted strings let you break the rules
- and more…
The original goes into interesting detail and there’s a lively discussion on r/programming:
More on the topic: