I am building a website for a client. There is a form on the website and the client would like that when the form is submitted, the content of the filled out form, is sent both to the client and also to the customer that filled out the form, so they have a record of what they filled out. I would like to avoid any paid third party apps. Is this possible?
Here is my site Read-Only: LINK
(how to share your site Read-Only link)
@Simon_Davis - Nope as this It is not a feature Webflow provides. If you want a notification sent to the submitter you need to use a third-party tool to handle it.
Yes there is a nodemailer JS I’m using outside of Webflow for email services. It requires coding knowledge, If you are not a developer your option is use paid service or hire developer to do this for you.
If you re not a developer not willing to pay you can always search internet if there is some tutorial and learn “how to”. 
here is link that should be used in WF as WF does not allow install npm packages.
rest is on you
Edit: here is one project in Svelte to get an idea how mailer is set (as in docs) if this will be any help. Im not familiar how to set .env file in WF
Basic connection setup
sending email to client and user