Disable Exchange server DNS Reverse Lookups


Exchange does a reverse DNS lookup for security reasons when an SMTP connection is established. If the reverse lookup fails to resolve, Exchange may drop the users connection.

To disable reverse lookup for Exchange, use the following Windows NT registry hack:

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\MSExchangeIMC\Parameters\
Name: DisableReverseResolve
Type: REG_DWORD
Value: 1

Note: This tip only applies to Exchange 5.5.

Related tip:

Traffic analysis tool for Microsoft Exchange server

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