1. What happens when the user submits the form, how do I access the data / know about new submissions?
When you setup a form you tell us who you'd like the form emailed to. When the forms submitted, we'll email that address the contents.
2. Am I able to customize the fields?
Absolutely! You're in full control of the form itself; what fields are there, how it's styled, where it's hosted. All you need to do is set the forms action to your sendfly.io url so that when the form is submitted it gets posted to us.
3. What happens if I go over 5000 submissions?
I haven't quite figured out that path yet; right now you'll just keep getting the submissions. I'll work on adding different plans, but wanted to keep it simple at launch. If you're interested and know you'll need more than 5,000 submissions let me know and we can work something out!