There are times in which you simply cannot (or should not) immediately reply to a message. However there are some social and professional messages that need at least something sent back to the other person, for both courtesy and acknowledgment. This is where an application called Can’t Talk from XDA Senior Member crazyfool_1 comes in handy as it enables you to set up auto-reply messages for a number of services including WhatsApp, Slack, Email, SMS and more. The developer does say that the app auto-reply features will become an in-app purchase once it leaves beta. But they will give those who are in the beta a promo code once the in-app purchase is added.
Check out Can’t Talk in our Apps and Games forum