Extension String {

Question

iOS Developers — русскоговорящее сообщество

Extension String {

public var isEmail: Bool {
let dataDetector = try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)

let firstMatch = dataDetector?.firstMatch(in: self, options: NSRegularExpression.MatchingOptions.reportCompletion, range: NSRange(location: 0, length: length))

return (firstMatch?.range.location != NSNotFound && firstMatch?.url?.scheme == "mailto")
}

public var length: Int {
return self.characters.count
}
}

это норм решение, детектит даже .рф домены