451 5.7.3 Cannot achieve Exchange Server authentication
I ran into this error recently while trying to migrate from Exchange 2003 to Exchange 2010. I had my Exchange 2003 and Exchange 2010 mailbox servers in coexistence and had successfully migrated a pilot group of users to the new server. Mail flow was still be directed through the Exchange 2003 server, although I did have a Send Connector on the 2010 server.
Users on both the 2003 and 2010 servers could send and receive mail externally. Users on the 2003 server could send messages to users on the 2010 server. However, users on the 2010 server could not send message back to the 2003 server. The queues would just fill up and 2010 users would receive a delivered delayed message. The error in the message queue was the one mentioned above.
The fix was two-part for me.
The first was IP restrictions that had been put in place on the Default SMTP Virtual Server properties. To get to these properties:
- Open Exchange System Manager on your Exchange 2003 server.
- Expand Administrative Groups.
- Expand the Exchange 2003 Administrative Group (most likely “First Administrative Group“)
- Expand Servers.
- Expand the hostname of your Exchange 2003 server.
- Expand Protocols.
- Expand SMTP
- Right-click Default SMTP Virtual Server and select Properties from the context menu.
- Select the Access tab.
- Select the Connection button
- If Only the list below check box is selected, then click Add and add the IP of your Exchange 2010 server under Single Computer.
- If All except the list below check box is selected, then make sure the IP of your Exchange 2010 server is not included in the list.
- Click Ok twice.
- Right-click the Default SMTP Virtual Server and select Stop.
- Right-click the Default SMTP Virtual Server and select Start.
The second part was the actual authentication of the Default SMTP Virtual Server.
- Open Exchange System Manager on your Exchange 2003 server.
- Expand Administrative Groups.
- Expand the Exchange 2003 Administrative Group (most likely “First Administrative Group“)
- Expand Servers.
- Expand the hostname of your Exchange 2003 server.
- Expand Protocols.
- Expand SMTP
- Right-click Default SMTP Virtual Server and select Properties from the context menu.
- Select the Access tab.
- Select the Authentication button.
- Make sure Integrated Windows Authentication is checked.
- Click Ok twice.
- Right-click the Default SMTP Virtual Server and select Stop.
- Right-click the Default SMTP Virtual Server and select Start.
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