During September 2025, Georg Sieber focused on backend and email development within the PHPMailer/PHPMailer repository, addressing a critical bug affecting S/MIME header encoding stability. He resolved issues with MIME header encoding order and boundary handling in signed messages, specifically targeting scenarios with long header lines that previously risked corruption or misinterpretation. Working primarily in PHP, Georg’s targeted fix improved the reliability and security of PHPMailer’s S/MIME workflow, reducing potential support issues and enhancing trust in email delivery. Although no new features were released, his work demonstrated depth in backend problem-solving and a strong understanding of secure email transmission protocols.