I added a contact form to my site and now I don’t know if I’m handling the data properly

This started as a simple static site, but now people are actually submitting inquiries with their names and emails. I’m currently just sending it through a simple endpoint, but I honestly don’t know where the data is stored or how secure it is. It feels fine at a glance, but I don’t want to assume. If you’ve handled this before, what setup did you use to safely collect and store form submissions without running a full backend?