A message has been received by the Exchange 2007 store but failed to reach the User. No NDR was received by sender or recipient. The sender successfully sent a mail through earlier in the day but recorded a different IP address.
Mail tracking reported following facts for the non delivered message:
Event ID #1 Receive Source: SMTP
Event ID #2 FAIL Source: Routing
Can you advise how I can take this further and understand where it failed?