Hi @Nir, one thing I would suggest, is to use an external mail service provider like Mailchimp. In order to receive forms on an exported site, the forms must be connected to some mail script or mail service.
See how to integrate to mailchimp here: MailChimp form Integration | Webflow University
Alternatively, if the hosting being used on the external server provides a mailscript solution, the forms can be pointed to the mail script, by changing the Action field to point to the mailscript url on your own server.
Ususally the hosting provider should provide instructions how to use their own mail script. If you can let me know which hosting provider is being used, I can see if there is any documentation available.