Exchange 2003 - Message stuck in the categorizer

If you have a big distribution list or email enabled security group within Active Directory which has a particular member that forwards an email externally, you might not be able successfully send an email to that group.

When you track the message using Exchange Message Tracking Center, you'll find out that the message is in the status: Message Submitted to Categorizer

This is because the automatic forward email is not enabled by default in Exchange 2003. To enable this:

• Go to Exchange System Manager
• Expand Global Settings
• Click Internet Message Formats
• Right click Default
• Click Advanced tab
• Choose Allow automatic forward

If this one does not work, try to do high level diagnostic with categorizer - modify the registry:

HLM\System\CurrentControlSet\Services\MSExchangeTransport\Diagnostics\

Change 2 Categorizer from 0 to 7

and check your application event log