You can set auto-responders informing your customers that you're successfully received their message and that they should expect your response shortly using Magento 2 Custom Form Builder Extension.

Read this How to Install and Configure Custom Form Builder to Magento 2 to setup this extension.

Here are the few more resource to help you get most out of this Magento 2 Custom Form Builder Extension.

• How to Set Up and Enable Contact Us Form in Magento 2
• How to Validate Forms in Magento 2
• How to Add a Custom Field in Magento 2 Registration Form
• How to Customize Contact Us Form in Magento 2 Website
• Steps to Add Multi-select UI Dropdown in UI Form in Magento 2
• How to Add Date of Birth Field in Customer Registration Form in Magento 2
• How to Create Admin Grid and Form without UI Component in Magento 2
• How to Create UI Component Grid and Form in Magento 2