Worked on the symfony/symfony repository to enhance the security and reliability of the Symfony Mail subsystem by refining the EsmtpTransport authentication method order. Focused on back end development using PHP and Symfony, the update prioritized the PLAIN authentication method over the legacy LOGIN, aligning with current security standards and reducing reliance on outdated protocols. The change was carefully implemented to maintain compatibility and minimize risk to existing workflows, with thorough documentation to support future maintenance. No major bugs were addressed during this period, as the primary emphasis was on feature refinement and protocol-level configuration for improved mail server interoperability.