Hotmail Email Availability Checker Script

I'm looking for a Python script that can check the availability of Hotmail emails using the requests library. The script should be able to work with a proxy list (ip:port format) from a file called proxy.txt, check against a list of emails from emails.txt, and utilize threading for efficient processing.

Key functionalities of the script:
- Save the results to a TXT file
- Skip to the next email if one is unavailable

The ideal freelancer for this project should have:
- Strong experience with Python, particularly the requests library
- Familiarity with threading in Python
- Prior experience with web scraping or checking email availability
- Ability to work with proxy servers

Please ensure that the script is efficient, reliable and well-commented for future reference.