marsspaceone/mail-checker-v1.0 ? reverse-engineered prompt

Build me a simple Streamlit app called Mail Checker.

I want a clean page where I can enter one or more email addresses and run a basic check on them, then see clear results right away in the browser. Make it feel polished and easy to use, with helpful messages for valid, invalid, and empty inputs. If you need to look up current docs online, feel free to do that.

Keep the app lightweight and straightforward, since this is just a small Python project. Add a nice title, a short description, an input area, and a results section that makes it obvious what passed and what failed. If it makes sense, include a sample input and a button to start the check. Please make sure it runs cleanly from the main Streamlit file and install any needed dependencies in the requirements file.