This archive contains proof of concepts and a whitepaper that describes multiple email client implementations where popular clients for email are vulnerable to signature spoofing attacks.
You can download it from the following link: https://packetstormsecurity.com/files/download/152703/Johnny-You-Are-Fired-master.zip
Source: https://packetstormsecurity.com/files/152703/Johnny-You-Are-Fired.html