The issue with Exchange has been addressed. We started a major project last Thursday involving the entire Exchange team to address series of expoits that have been documented in the wild and could pose threat: https://swarm.ptsecurity.com/attacking-ms-exchange-web-interfaces/
The actual issue that caused a problem was unrelated, in one piece of infrastructure suddenly failing Microsoft Health checks for proxying requests to the backend. While this was resolved quickly, diagnosing it took a while. All users had access to ExchangeDefender LiveArchive during the work and all services are back to normal.
Update 07/27/2020 13:58 PM 24 days
The issue with OWA/EWS has been addressed, and all users that were on the impacted are now reporting connectivity and routing is back to normal.
Update 07/27/2020 13:38 PM 24 days
Some users reported they are having issues connecting to OWA and Outlook. We are investigating what could be causing the issue, please stand by.
We'll update this SA as soon as we have more information.
Thank you for your patience.