Outlook Web App (OWA) is Microsoft’s browser-based interface for accessing email, calendars, and other mailbox features hosted on Exchange. It lets users work with their mail without installing the Outlook desktop application.
Because OWA depends on Exchange services and the underlying server’s identity and network components, failures in those layers can prevent sign-in or mailbox access even when OWA itself was not changed. In security operations, defenders monitor OWA availability and authentication logs to distinguish service disruptions from suspicious access attempts. During maintenance, checking sign-in and mail flow after server updates can help identify problems early.