Customer.io - We make it easy to send emails triggered by user behavior. Build, measure and improve your emails to activate and retain users
Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
Customer.io Slack Action - Send notifications into Slack, based on user activity
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.
Jotform - Free Online Form Builder & Form Creator
Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.