How can I stop the Exchange SMTP service performing reverse lookups?

A. Some SMTP hosts do a reverse Domain Name Service (DNS) lookup for security reasons when an SMTP connection is established. If this reverse lookup fails to resolve properly, they will possibly drop the connection.

To disable reverse lookup for Exchange perform the following:

1. Start the registry editor (Regedit.exe)
2. Move to HKEY_LOCAL_MACHINE\System|CurrentControlSet\Services\MSExchangeIMC \Parameters\
3. Double click on DisableReverseResolve (or create of type DWORD if not there)
4. Set the type to binary and enter 1. Click OK
5. Close the registry editor

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