The Delivery Message purchase action is pretty self explanatory, it allows you to add a message to be delivered upon the successful purchase of a product.
You can use this action to give special instructions, tell the customers thank you, post a URL, even give discount codes for future purchases. Basically if there's any extra info you want to give your customers the Delivery Message action is one of the best ways to do it.
To add a Delivery Message to your product follow the steps below:
1- Select Products from the left menu of your DPD dashboard
2- Click the product you want to add it to
3- Select Manage Purchase Actions from the products details page
4- Select to add a Delivery Message purchase action as shown in the screenshot below:
Configure the message to say whatever you like and be sure to Save at the bottom of the page when you're done.