Exchange Server 2016 and Office Online Server Process Flow

Here is the process flow of how Exchange Server handles attachments when integrated with Office Online server.

  1. Exchange uses discovery URL to ask Office Online Server which files types it can view and edit.
  2. Office Online Server returns table of supported file types.
  3. User opens mail with attachment that matches one of the file types Office Online Server supports and OWA requests document URLs for supported types.
  4. Exchange builds URL with Auth token, app URL, and Attachment ID and returns it to OWA.
  5. User clicks attachment within OWA and spawns an iFrame on client to load the URL returned by Exchange.
  6. Office Online Server retrieves document content from Exchange.
  7. 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.