Developed an enhancement for the gchq/CyberChef repository focused on improving domain extraction in cybersecurity workflows. The work introduced support for underscores in DMARC and DKIM domains by implementing a new regular expression, DMARC_DOMAIN_REGEX, and exposing it as an optional argument within the ExtractDomains operation. This JavaScript-based solution enables more comprehensive and accurate extraction of domains, particularly those relevant to email authentication protocols, thereby reducing the need for manual post-processing. The update leveraged expertise in regular expressions and domain extraction, addressing a nuanced requirement in security operations and contributing to more robust and automated domain discovery within CyberChef.