Swift method to check for a valid email address (uses Apples data detector instead of a regex)

String+Email.swift

extension String {
    func isValidEmail() -> Bool {
        guard !self.lowercaseString.hasPrefix("mailto:") else { return false }
        guard let emailDetector = try? NSDataDetector(types: NSTextCheckingType.Link.rawValue) else { return false }
        let matches = emailDetector.matchesInString(self, options: NSMatchingOptions.Anchored, range: NSRange(location: 0, length: self.characters.count))
        guard matches.count == 1 else { return false }
        return matches[0].URL?.scheme == "mailto"
    }
}

Swift 5:

extension String {
    func isValidEmail() -> Bool {
        guard !self.lowercased().hasPrefix("mailto:") else {
            return false
        }
        guard let emailDetector
            = try? NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue) else {
            return false
        }
        let matches
            = emailDetector.matches(in: self,
                                    options: NSRegularExpression.MatchingOptions.anchored,
                                    range: NSRange(location: 0, length: self.count))
        guard matches.count == 1 else {
            return false
        }
        return matches[0].url?.scheme == "mailto"
    }
}