6.) Bienvenido/a a John Doe. Por razones técnicas no podemos atender su llamada. Si lo desea, puede escribirnos un correo electrónico a [email protected]. Uno de nuestros empleados le contestará lo antes posible. Disculpe las molestias. Gracias por su comprensión.
You can also make use of a 3rd party option and use a crowdsourcing professional voicemail greeting provider such as Fiverr to record your voicemail greeting. Fiverr is flexible, fast and affordable and at just $5, you have the option of choosing between hundreds of professional voice-over actors who can record your script. You can also find professionals who can record voicemail greetings in various languages, accents, etc. at very affordable prices and deliver the recording within 3 working days or less.

If someone takes the time to call and leave you a voice message, they usually have a reason that they are calling. It does convey a certain level of interest when someone is willing to hop on the phone with you. If they were less interested, they would probably send you an email or fill out a form on your website.
You could add the words "After-Hours Service" or "After-Hours Line" after the company's name. That way there's no concern over whether it is indeed a number that reaches a real person who will return their call during non-business hours. It's a way to let them know they're on the right track. If that makes sense. :)