Given that the compiler can't enforce that users only enter valid data at compile time, the next best thing is enforcing that when they do enter invalid data, the program won't produce an `Email` object from it, and thus all `Email` objects and their contents can be assumed to be valid.

This is all pretty language-specific and I think people may end up talking past each other.

Like, my preferred alternative is not "return an invalid Email object" but "return a sum type representing either an Email or an Error", because I like languages with sum types and pattern matching and all the cultural aspects those tend to imply.

But if you are writing Python or Java, that might look like "throw an exception in the constructor". And that is still better than "return an Email that isn't actually an email".