I installed a new Exchange 2010 Server into our network and decommissioned the old Exchange server, the new server had a different IP address.
The SMTP service in IIS needs to be configured with correct IP. This has only become an issue due to the Exchange Server changing its IP and the SMTP Service being configured initially with the old IP.
Admin Tools>>>(IIS) 6.0 Manager.
• Drill down and right-click the SMTP Virtual Server (e.g. [SMTP Virtual Server #1]) and select properties.
• Click on the Delivery tab and then the Advanced button.
• Change the Smart Host details to correct IP.
All the emails in the queue will now be automatically delivered.