Across the world, companies rely on Microsoft and Google to administer email accounts for employees. Keeping all those mailboxes secure, however, is a business opportunity.Proofpoint went public in 2012, and as enterprises migrated to the cloud, many adopted the company's secure email gateway software as a precautionary measure. But private equity firm Thoma Bravo bought Proofpoint in 2021, and another provider, Mimecast, went private in 2022.Then generative artificial intelligence took off. The trending te ...