This applies when you experience HTTP status code error500 when importing an iCalendar file from Outlook/Exchange.

Microsoft refuses to serve content to “unknown” HTTP clients (started on 18th August 2025).
Open settings and paste the following content into the user-agent field:
Mozilla/5.0 (Android 16; Mobile; rv:142.0) Gecko/141.0 Firefox/141.0
The user-agent is taken from this website: https://www.whatismybrowser.com/guides/the-latest-user-agent/firefox

Problem should be fixed on the next import.

Posted in: Import