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When a message is sent to an encapsulated Simple Mail Transfer Protocol (SMTP) one-off address through an Internet Mail Service that is configured so it does not reroute SMTP messages, the message may still be rerouted. Encapsulated SMTP one-off addresses contain the IMCEASMTP prefix.
To resolve this problem, obtain the latest service pack for Exchange Server version 5.5. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
191014 XGEN: How to Obtain the Latest Exchange Server 5.5 Service Pack
The English version of this fix should have the following file attributes or later:
Component: Internet Mail Service
Microsoft has confirmed that this is a problem in Microsoft Exchange Server version 5.5. This problem was first corrected in Exchange Server 5.5 Service Pack 3.
After you apply the fix, if rerouting is disabled, the Internet Mail Service returns all messages that are sent to an encapsulated SMTP one-off address. If rerouting is enabled, but one or more routing restrictions have been defined, the messages are rerouted or returned based on these restrictions.If you are using the Internet Mail Service as a site connector, rerouting must be enabled after the fix is applied. The Internet Mail Service must be able to reroute messages addressed to recipients that are homed on the bridgehead server in the other site.
In addition, you should check the list of IP addresses that are allowed to relay through your server and make sure that it's updated. This is because one side effect of this problem is that it could allow incorrectly-configured sites to operate correctly in some situations where the Internet Mail Service is used as a site connector.
For example, suppose you intended to allow a server whose IP address is 192.168.0.1 to relay mail through your server using the Internet Mail Service as a site connector. This problem would allow the server to relay mail through your server even if you had not added 192.168.0.1 to the list of IP addresses that are authorized to do so. If you then apply the fix, you would find that mail relaying from 192.168.0.1 no longer works. However, you could restore proper functionality by adding 192.168.0.1 to the list of approved servers. To do so, view the properties for the Internet Mail Service, click the Routing tab, click Routing Restrictions, and then add the server's IP address or subnet address.
To configure the Internet Mail Service so it does not reroute SMTP messages:
Start the Microsoft Exchange Server Administrator program. To do so, click Start, point to Programs, point to Microsoft Exchange, and then click Microsoft Exchange Administrator.
In the left pane, click the Connections object under the appropriate site. In the right pane, click the Internet Mail Service, and then on the File menu, click Properties. Note that the Connections object appears under the Configuration object.
Click the Routing tab, select Do not reroute incoming SMTP mail, and then click OK.
When the Internet Mail Service is configured in this manner, messages addressed to recipients that are listed in the global address list are delivered, but all other messages are normally returned with a non-delivery report (NDR).