• Users are complaining about receiving non-delivery reports when they send messages.
  
  Select this symptom if messages bounce and non-delivery reports (NDRs) are returned to the senders. NDRs may be returned from outside the corporate Exchange organization or inside the Exchange organization. The Exchange Mail Flow Troubleshooter will try to guide users in determining the correct troubleshooting steps for this symptom. Be aware that because it is possible that the root causes are outside Exchange Server, the troubleshooting guidance is very important.
  
  
• Messages coming from external senders over the Internet are delayed or are not received by some recipients.
  
  This and the next symptom are similar. Select this symptom if the messages are not coming into the corporate Exchange Server organization, or the messages are not coming through the non-Exchange gateway servers at the boundary. The Exchange Mail Flow Troubleshooter will examine both inside the Exchange Server organization, and the gateway.
  
  
• Messages that are destined for external recipients on the Internet are delayed or are not sent to some recipients.
  
  Select this symptom if the messages that are supposed to be delivered outside the corporate Exchange Server organization are staying in the corporate Exchange Server organization, or the messages cannot go through the non-Exchange gateway servers at the boundary. The Exchange Mail Flow Troubleshooter will examine both inside the Exchange Server organization, and the gateway (as it did in the previous symptom).
  
  
• Messages are backing up in one or more queues on a server.
  
  Select this symptom if messages are staying in Exchange Server queues, notably, the Remote Delivery Queue, the Awaiting Directory Lookup Queue, and the Local Delivery queue. The backup affects the messages that are routed in the same Exchange Server organization in addition to the messages that are coming from and going to the Internet, depending on the path where messages are routed. Working on this symptom could then possibly address the second and third issues in this list of symptoms.
  
  
• Users are reporting that messages are backing up in their Outbox (for Exchange Server 2007 only).
  
  Select this symptom if messages are staying on the user's mailbox server and are not being transferred to other servers. The Exchange Mail Flow Troubleshooter will try to look at both the Mailbox role and the Hub Transport role.
  
  

After you have chosen a symptom, you will be asked for server and user information, and then the analysis starts. When the Exchange Mail Flow Troubleshooter has completed its analysis, a list of recommendations is shown on the result page.