ConvertKit
ConvertKit is an email marketing platform that helps you send customized emails to your customers. It helps you send well-timed and accurately targeted email content to your subscribers.
By integrating your forms.app and ConvertKit accounts, you can create a subscriber record and segment your customers by adding tags to your subscribers. You can also add a purchase record to your subscriber profiles.
You might also like

HubSpot CRM
Connect your forms to HubSpot and automatize your processesNativeZapier

SharpSpring
Streamline new contacts to your emailing list from your form responses and automate your work.Zapier

Any.do
Create notes for events or meetings with your form responses.Zapier

SmartReach
Streamline new contacts to your emailing list from your form responses and automate your work.Zapier