This idea has been merged into another idea. To comment or vote on this idea, please visit ENTCOM-I-49 SMS / Text Auto Responder.
It is very surprising this isn't already built in and would be a crucial feature.
EX: When out of office, being able to alert any inbound calls/texts that you are out of office and provide any other contact details.
Any other Phone SMS app/device has this feature so adding it would be greatly appreciated