Here is the process flow of how Exchange Server handles attachments when integrated with Office Online server.
- Exchange uses discovery URL to ask Office Online Server which files types it can view and edit.
- Office Online Server returns table of supported file types.
- User opens mail with attachment that matches one of the file types Office Online Server supports and OWA requests document URLs for supported types.
- Exchange builds URL with Auth token, app URL, and Attachment ID and returns it to OWA.
- User clicks attachment within OWA and spawns an iFrame on client to load the URL returned by Exchange.
- Office Online Server retrieves document content from Exchange.
- Office Online Server renders content in web client (e.g., Word Web App).
Logs to Troubleshoot:
- Event Viewer logs on both Office Online Server and Exchange.
- Component Logging file on Exchange Servers.
- Client side traces -> F12 or Fiddler.
- ULS Logs located on OOS Server.