On: The Correct Way to Validate Email Addresses

[danso]

How about more than one @ sign? Does the email address spec exclude the possibility of more than one @ symbols?

[tempestn → danso]

It doesn't matter. If they have typed an @, they probably understand that it's an email field. Trying to validate to the spec beyond that is pointless, for reasons thoroughly covered in the article.

[kej → danso]

Nope, that's valid if one of them is quoted: "very.unusual.@.unusual.com"@example.com

[ediblenergy → danso]

It actually used to (maybe still does) signal routing information[1]. An example from the RFC is "@ONE,@TWO:JOE@THREE" [1]: https://tools.ietf.org/html/rfc821

[zeveb → danso]

The local-part may contain a quoted @: "@"@example.invalid is a valid email address.

@ signs are also permitted in comments: (ted@home)ted@example.invalid is also a valid email address.