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Enabling SMTP Vrfy in Exchange 5.5, 2000 & 2003

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  • Enabling SMTP Vrfy in Exchange 5.5, 2000 & 2003


    I am looking for a way to enable the SMTP Vrfy command in Exchange 2000 and 2003.

    In Exchange 5.5, SMTP Vrfy can be easily enabled with a Windows registry entry:
    Navigate to:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\MSExchangeIMC\Parameters
    and add the following value:
    Value name: EnableVRFY
    Data type: REG_DWORD
    Data: 0x1 (to enable)

    As a first step I found the way to configure Exchange 2003 to check recipients in SMTP protocol
    This is not available in Windows 2000.

    To prevent Email address harvesting, Exchange 2000 and 2003 disable SMTP Vrfy, and return instead:
    > vrfy [email protected]
    252 2.1.5 Cannot VRFY user, but will take message for <[email protected]>

    This is confirmed by the microsoft support page: XIMS: VRFY Command Does Not Work in Exchange 2000 or in Exchange 2003;en-us;289521
    This pages states that one need to write a 'protocol event sink' to do it.

    The architecture is detailed at the page: Chapter 6: SMTP Transport Architecture in the paragraph SMTP Configuration Settings in the Metabase

    SMTP events are described in MS Windows 2000 SMTP Service Events

    Another article: How to turn off ESMTP verbs in Exchange 2000 Server
    and in Exchange Server 2003 describes how to enable/disbaled some SMTP commands.
    This is confirmed by the article listing Metabase S options (IIS metabase properties

    The article Using the Metabase Reference Pages listed a range of values defining the protocol behaviour, like:

    Internal ID

    Each property has a unique numerical identifier which IIS recognizes
    internally. This is useful when writing C/C++ applications that use ABO.

    Identifiers used by IIS are assigned from a pool of reserved numbers. If you create new identifiers in the metabase, use identifier numbers greater than 65535 (0x0000ffff) to avoid conflicts with current or future system data.
    Identifiers are defined in the IIScnfg.h header file. The following ranges are reserved by IIS:

    Range Reserved for
    1 (0x00000001) to 32767 (0x00007fff) IIS identifiers.
    28672 (0x00007000) to 32767 (0x00007fff) The subset of ASP identifiers.
    32768 (0x00008000) to 36863 (0x00008fff) FrontPage Server Extensions identifiers.
    36864 (0x00009000) to 40959 (0x00009fff) SMTP identifiers, owned by Exchange.
    40960 (0x0000a000) to 45055 (0x0000afff) POP3 identifiers, owned by Exchange.
    45056 (0x0000b000) to 49151 (0x0000bfff) NNTP identifiers, owned by Exchange.
    49152 (0x0000c000) to 53247 (0x0000cfff) IMAP identifiers, owned by Exchange.
    53248 (0x0000d000) to 57343 (0x0000dfff) MSCS identifiers.
    57344 (0x0000e000) to 61439 (0x0000efff) Application Center identifiers.

    It looks like the Windows SMTP server protocol behaviour can be defined by values (SmtpInboundCommandSupportOptions ?) either in the metabase IIS, or in the Active Directory configuration if installed.

    Unfortunately I haven't found much more.

    Does anybody know how to enable the SMTP Vrfy command in Exchange 2000 and 2003 ?