During the migration to Exchange 2010 you might have the need to keep your Exchange 2003 server up and running. This is a supported configuration but sometimes you can run into problems even though everything is technically configured correctly.

In our case our send connectors and routing group connectors were perfectly fine. Yet people on Exchange 2010 couldn’t email Exchange 2003 users via Outlook. Now the stranger thing was they could using OWA.

Well the problem had to do with Event ID: 9667:

Event ID: 9667

Type: Error

Category: General

Source: msgidNamedPropsQuotaError

Description: Failed to create a new named property for database “” because the number of named properties reached the quota limit (). User attempting to create the named property: . Named property GUID: . Named property name/id: .

So to fix the problem we had to follow these steps:

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\\Private-*************
• Modify the following registry vaule: NonMAPI Named Props Quota
• Change the value from 8192 to 16384
• Dismount and remount the store