KianSantang777/mailaccess_checker ? reverse-engineered prompt

Build me a simple Python tool that takes a text file of email addresses and checks which ones look valid and which ones have common issues, like bad format, missing domain, or unreachable mail domain.

I want it to process a list in parallel so it finishes fast, and save a clear log file with the results of each line. Make it easy to run from the command line, ask me for the input file path, then print a short summary of how many were valid, invalid, and had errors.

If you need to look up current docs or best practices online, go ahead. Please keep it clean, reliable, and easy to understand, with good error handling and a simple output file I can review later.