JOOMLA PHP DEVELOPMENT to customize 2 web forms

Our JOOMLA site is already running with the newsletter component Acymailing. We need to save email addresses in a newsletter subscriber table. Your work is to write some code to test the validity of the email adresses. (NO DUPLICATION). Those 2 forms are built with RsForm!Pro. We extract the email field from the forms to save them in the acymailing suscriber table with a RSForm!Pro mapping plugin. We want to get rid of registering duplicate emails. Your work is to ensure that the email address doesn't already exist in the newsletter subscriber table. You need to test if the email is a new one before adding it to the newsletter subscriber table. That's it.