Python Mailbox Email Checker

I need a tool that can perform full-mailbox validation—far beyond simple syntax or MX checks—specifically for addresses at Norton, Coinbase, huntington.com, and Regions.com. The solution has to run in Python and must work in two modes: real-time look-ups (single address calls) and large batch jobs. In practice I need it to cope with traffic spikes of roughly 100 000 addresses without timing out or being throttled.

Seeking an experienced Python developer to build a robust Mailbox Email Checker tool that verifies emails for popular platforms such as Norton, Coinbase, huntington.com, and Regions.com. The ideal candidate will design and implement scripts to automate mailbox access and email validation across these services, ensuring accuracy and reliability. Strong Python skills and familiarity with email protocols are required for this project.

Please deliver the well-documented Python source, a quick setup guide, and a short note on any dependencies or third-party libraries you decide to use so I can reproduce the environment exactly.