Internet Mail Service Extension (Imsext.dll) has several functions. This article covers the append and prepend capabilities of this dynamic-link library (DLL). Message journaling is also a capability of Internet Mail Service Extension, but message journaling is not covered in this article. For additional information about message journaling, click the article number below to view the article in the Microsoft Knowledge Base:

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Installing Internet Mail Service Extension

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To install Internet Mail Service Extension (Imsext.dll):

1.	To copy the Internet Mail Service Extension to your server, do one of the following: • Locate the Internet Mail Service Extension in the following folder: Exchsrvr\Connect\Msexcimc\Bin • Locate the Internet Mail Service Extension included in the BackOffice 4.5 Resource Kit.
2.	Register Internet Mail Service Extension by typing the following at the command prompt: regsvr32 imsext.dll
3.	To enable Internet Mail Service Extension in Exchange Server 5.5 Service Pack 1 or later without losing routing table capability, you need to create a registry value:NOTE: Microsoft recommends the following method to enable Internet Mail Service Extension. a. Start Registry Editor (Regedt32.exe). b. Locate the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\Parameters c. On the Edit menu, click Add Value, and then add the following registry value: Value Name: NonRoutingExtensionDll Data Type: REG_SZ String Value: The full path of the Internet Mail Service Extension utility DLL You can also enable Internet Mail Service Extension in the Exchange Server Administrator program by opening the Internet Mail Service properties, clicking the Routing tab, and then selecting Internet Mail Service Extension as the custom routing program. IMPORTANT: Microsoft does not recommend this method. You will lose routing table capability.
4.	Create an Extension registry key: a. Locate the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\Parameters b. On the Edit menu, click Add Key, and then type Extension. c. Quit Registry Editor.

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Inbound SMTP

To add prepended text to the body of an inbound Simple Mail Transfer Protocol (SMTP) message, create an InboundPrepend registry value:

1.	Start Registry Editor (Regedt32.exe).
2.	Locate the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\Parameters\Extension
3.	On the Edit menu, click Add Value, and then add the following registry value: Value Name: InboundPrepend Data Type: REG_SZ String Value: The text that you want to prepend to incoming messages.
4.	Quit Registry Editor.

To add appended text to the body of an inbound SMTP message, create an InboundAppend registry value:

1.	Start Registry Editor (Regedt32.exe).
2.	Locate the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\Parameters\Extension
3.	On the Edit menu, click Add Value, and then add the following registry value: Value Name: InboundAppend Data Type: REG_SZ String Value: The text that you want to append to incoming messages.
4.	Quit Registry Editor.

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Outbound SMTP

To add prepended text to the body of an outbound SMTP message, create an OutboundPrepend registry value:

1.	Start Registry Editor (Regedt32.exe).
2.	Locate the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\Parameters\Extension
3.	On the Edit menu, click Add Value, and then add the following registry value: Value Name: OutboundPrepend Data Type: REG_SZ String Value: The text that you want to prepend to outgoing messages.
4.	Quit Registry Editor.

To add appended text to the body of an outbound SMTP message, create an OutboundAppend registry value:

1.	Start Registry Editor (Regedt32.exe).
2.	Locate the following key in the registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIMC\Parameters\Extension
3.	On the Edit menu, click Add Value, and then add the following registry value: Value Name: OutboundAppend Data Type: REG_SZ String Value: The text that you want to append to outgoing messages.
4.	Quit Registry Editor.

You must restart the Internet Mail Service for these changes to take effect. You must also restart the Internet Mail Service if you change the text string.

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