A bit of refactoring

[Luciano Berardi]

Hi, there is a specific reason to duplicate the code in the 2 validation function? The Validate function does exactly what the FastValidation does plus the MX lookup. My 2 cents for the Validate function:

func Validate(email string) error {
	fastValidationErr := ValidateFast(email)
	if fastValidationErr != nil {
		return fastValidationErr
	}

	at := strings.LastIndex(email, "@")
	host := email[at+1:]

	switch host {
	case "localhost", "example.com":
		return nil
	}

	if _, err := net.LookupMX(host); err != nil {
		if _, err := net.LookupIP(host); err != nil {
			// Only fail if both MX and A records are missing - any of the
			// two is enough for an email to be deliverable
			return ErrUnresolvableHost
		}
	}

	return nil
}

[Luciano Berardi]

Actually I think you could completely separate the SyntaxValidate from the DomainValidate. In case both of those are called.

Thanks

[Vojtech Vitek (golang.cz)]

@lucio81 I think you're right. Mind sending a PR to improve this pkg?