Only BurpSuite Professional has the collaborator, and costs a lot. ZAP does not include OAST functionality. And there are alternatives:
pingb.in was originally for capturing ICMP pings with a unique payload, it works great for DNS and HTTP too. It does not seem to support HTTPS though.
The Webhook.site supports inspecting, testing and automating (with the visual Custom Actions builder, or WebhookScript) incoming HTTP request sor e-mail.
Interactsh is an open-source tool for detecting out-of-band interactions. It is a tool designed to detect vulnerabilities that cause external interactions. Also see app.interactsh.com.