Building MailSink: a temp email API with MCP server on Cloudflare Workers

The problem Testing email flows in CI has been painful for years. MailSlurp is $79/mo, Mailtrap's API isn't built for AI agents, and most alternatives want you to run your own SMTP server. I wanted something different: a REST API callable from tests, with an MCP server so AI agents could run email-verified signup flows natively. So I built it. What it does MailSink gives you programmatic temporary email inboxes via a simple REST API: # Spin up a disposable inbox curl -X POST api.mailsink.dev/v1/