XCON: The DSFlags key and the Message Categorizer (231730)

SUMMARY

The Message Categorizer in Microsoft Exchange 2000 Server is tasked with the handling of every message that comes into, or goes out of, the SMTP server, and determining what to do with it. The messages may be destined for the local store, a remote host through the message transfer agent (MTA), or a remote host through SMTP. The Message Categorizer also handles distribution list (DL) expansion.

The Message Categorizer can distinguish between local and remote, as well as between sender and recipient. The value of the DSFlags key is an indication of what the Message Categorizer is set to resolve. Each virtual server instance can be set to have a different value for the DSFlags key.

MORE INFORMATION

The Message Categorizer is included in the Windows 2000 operating system. Using the DSFlags key, the Message Categorizer can be configured to resolve only certain categories. The table below shows the values for the DSFlags key and the associated resolution capability of the Message Categorizer.

DSFlag value	Message Categorizer capability
0x1	Resolve Local Only
0x2	Resolve Remote Only
0x4	Resolve Sender Only
0x8	Resolve Recipient Only
0xF	Resolve All

On a server that has only Windows 2000 installed, the DSFlags key is set to a value of 9 (0x9). When Exchange 2000 is installed on the server, the DSFlags key is automatically set to a value of 15 (0xF). The table below shows the implication of these values:

Categories	DSFlags value	DSFlags value
Windows 2000 only	0x9	Resolve Local and Sender only
Windows 2000 with Exchange 2000	0xF	Resolve All

Note The Message Categorizer has to be in the enabled state (DSUseCat set to 0xFFFFFFF) for it to function. By default, Windows 2000 has the Message Categorizer set to the disabled state.

The DSFlags key value can be accessed in the Metabase at the following location:

/smtpsvc/Virtual Server Instance/RoutingSources

The following is an example of a Metabase dump for the RoutingSources of a virtual server instance. It shows the value of the DSFlags key after Exchange 2000 is installed on a Windows 2000 server.

DSUseCAT              : [IS]    (DWORD)    0xFFFFFFFF={-1}
DSFlags               : [IS]    (DWORD)    0xF={15}
DSPort                : [S]     (DWORD)    0x0={0}
DSType                : [IS]    (STRING)   "LDAP"
Account               : [IS]    (STRING)   "Administrator"
DSDomain              : [IS]    (STRING)   "TROLL"
KeyType               : [IS]    (STRING)   "IIsSmtpRoutingSource"
BindType              : [S]     (STRING)   "Simple"
SchemaType            : [S]     (STRING)   "NT5Exchange"

Important The Exchange code relies on the value of the DsFlags key being set to 196623 (0x3000F). Because of this reliance, Microsoft recommends that you do not change the default setting for this key. The flag tells the categorizer which domains to resolve against the DS (local, non-local, none, etc.).