Hi, In order to capture the leads there are various lead magnet plugins available in the market https://automationagency.com/best-wordpress-plugins-capture-leads/ you can check these based on your requirement which does their job very well. After that you need to customise a bit to email the user.
Other way round, you can capture the leads into Mailchimp, hubspot and then schedule the newsletter or offer to be sent out. Recently I have studied this which is also good to use https://mailster.co/