Peter Bauer and Neil Murray, two South African expatriates based in London, founded Mimecast in 2003 after recognising the growing vulnerabilities in corporate email as businesses became ever more dependent on digital communications. Peter had cut his teeth as a Microsoft systems engineer in the mid-1990s before moving to the UK, where he and Neil set about building a cloud-based platform to protect, manage, and archive email for enterprises.

From its London base, Mimecast grew into one of the world's leading email security companies, expanding aggressively into North America and listing on NASDAQ in November 2015. Dawn was an early and important institutional investor, supporting the company through a period of transformational growth during which Mimecast went from under $10m of revenue to a global cybersecurity leader.