Worked on the civicrm-core repository to address a critical memory leak in the Bulk Mailing System, focusing on backend development and performance optimization using PHP. Delivered a targeted bug fix that introduced explicit resource cleanup after each email, batch-level garbage collection, and streamlined header management to reclaim memory efficiently. These changes stabilized long-running cron processes, enabling reliable bulk mail campaigns for tens of thousands of recipients without memory exhaustion. The approach emphasized careful memory management and predictable resource reuse, improving code maintainability and reducing the risk of out-of-memory errors during large-scale mailings while supporting scalable, high-volume outreach operations.