When accessing Outlook Web Access I get an unusual error in Firefox: Corrupted Content Error The site at https://outlook.office.com/mail/inbox has experienced a network protocol violation that cannot be repaired. The page you are trying to view cannot be shown because an error in the data transmission was detected. This is apparently known by Microsoft. Via https://status.office365.com Title: Unable to access Microsoft 365 services or features User impact: Users may be unable to access Microsoft 365 services or features. Current status: We're analyzing system logs in order to better understand the issue and to determine our next troubleshooting steps. Scope of impact: Impact is specific to a subset of users who are served through the affected infrastructure. Next update by: Tuesday, July 2, 2019, at 10:30 PM UTC Switching to a VPN that has IPv6 connectivity and everything works (both desktop client and OWA). But that also changed my IPv4 address also so I can't conclude too much (but definitely see v6 communication to MS).