Event ID 1091 is logged, and intersite directory replication does not occur between an Exchange Server 5.5 computer and the Site Replication Service on an Exchange 2000 or Exchange 2003 computer

When you configure intersite directory replication between a Microsoft Exchange Server 5.5 computer and the Site Replication Service (SRS) on a Microsoft Exchange 2000 Server or Microsoft Exchange Server 2003 computer, the replication process from Exchange Server 5.5 to the SRS on the Exchange 2000 or Exchange 2003 computer is not successful. Additionally, the following event is logged in the application event log on the Exchange 2000 or Exchange 2003 computer:

Event ID: 1091
Category : None
Source : MSExchangeSRS
Type : Warning
Date: Date
Time: Time
Computer : SRS server name
Description :
The directory replication agent (DRA) attempted to open mail with name /o=EXCHANGE/ou=SITE/cn=Configuration/cn=Servers/cn=SRS server name /cn=Microsoft DSA: SRS server name but received error 2147746065. Messages could not be sent. Make sure that the mail service on this Microsoft Exchange Server computer is running.

This issue occurs because the Request for Response (RFR) service is disabled on the Exchange 2000 or Exchange 2003 computer. In intersite directory replication, Exchange sites use e-mail messages to transfer the directory objects for replication from one site to another. The local Exchange site places all the directory objects in an e-mail message and then sends this e-mail message to the remote site by using the Message Transfer Agent (MTA).

In a mixed Exchange server environment, the Exchange Server 5.5 site sends an e-mail message that contains the directory objects for replication to the remote Exchange 2000 or Exchange 2003 site. The SRS on the Exchange 2000 or Exchange 2003 computer then uses the DSProxy service to contact the global catalog server for its logon. The DSProxy service then sends a referral back to the SRS for its communication with the Active Directory directory service. Afterward, the SRS communicates directly with the global catalog server. If the RFR service is disabled on the Exchange 2000 or Exchange 2003 computer, Exchange 2000 or Exchange 2003 cannot provide a referral to the SRS. Therefore, the SRS cannot communicate directly with the global catalog server to replicate the directory information. The logon to the SRS mailbox is not successful, and replication does not occur.

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To resolve this issue, you must enable the RFR service on the Exchange 2000 or Exchange 2003 computer. To do this, follow these steps:

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeSA\Parameters
3. In the right pane, double-click the No RFR Service registry entry.
4. Under Base, click Decimal.
5. In the Value data box, type 0, and then click OK.
6. Quit Registry Editor.
7. Restart your computer.

For additional information about the RFR service in Exchange 2000, click the following article numbers to view the articles in the Microsoft Knowledge Base: