VaultSandbox

VaultSandbox is an open-source email testing tool that lets developers test email functionality in a production-like environment without relying on mock data or fake email services. Instead of stubbing out email delivery, it provides a real sandbox where you can send, receive, and inspect emails just as they would behave in production. The tool is designed for developers and QA teams who need to validate email workflows, templates, and integrations without risking actual user inboxes. By eliminating mocks, you get genuine email behaviour to catch formatting issues, delivery problems, and template rendering errors that mocks often miss. Since VaultSandbox is open-source, you can self-host it, inspect the code, and integrate it directly into your testing pipeline. This makes it particularly useful for teams that prioritise transparency, control over their test infrastructure, or need email testing as part of their continuous integration process.