Topic Last Modified: 2006-05-17

The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine whether the value for the msExchSmtpInboundCommandSupportOptions attribute for each instance of a Simple Mail Transfer Protocol (SMTP) virtual server is configured to support the default extended SMTP verbs for incoming connections.

These extended SMTP verbs are listed in the table below. If the Exchange Server Analyzer finds that any one of the listed default extended SMTP verbs for incoming connections is not supported, the Exchange Server Analyzer displays a warning.

Exchange Server 2003 uses these Exchange-specific extended SMTP verbs to communicate with other Exchange servers in the organization more efficiently than over standard SMTP. These verbs are controlled in the metabase and in Exchange Server event sinks. In Exchange Server 2003, the DS2MB process is responsible for updating the values in the metabase by copying the values from Active Directory. When you disable the event sinks, you may hinder Exchange Server performance.

Extended SMTP Verb Comments


Indicates that the local SMTP virtual server supports eight-bit MIME messages.


An alternative to the DATA command. This takes two arguments. When an SMTP virtual server responds to the EHLO keyword with CHUNKING, the SMTP server indicates that it supports the BDAT command and will accept messages in chunks.

  • The first argument indicates the length of the binary data packet. Therefore the SMTP host does not have to continuously scan for the end of the data. The receiving server counts the bytes in the message. When the message size equals the value sent by the BDAT command, the server assumes that it has received all the message data.

  • The second argument indicates whether the data packet is the last packet in the current transmission. The second argument is optional.


Indicates that the SMTP virtual server accepts messages that contain binary material without transport encoding by using a BODY parameter with a value of BINARYMIME with the MAIL command. When the SMTP server accepts a MAIL command that has a BODY parameter of BINARYMIME, the server agrees to preserve all bits in each octet passed using the BDAT command. The BINARYMIME SMTP extension can only be used with CHUNKING.


An ESMTP command that enables delivery status notifications as defined in Request for Comments (RFC) 1891.


Indicates that the SMTP server provides enhanced error status codes. The text part of all SMTP status responses, other than the initial greeting and any response to HELO or EHLO, is prefaced with a status code as defined in RFC 1893.


Sent by an SMTP server to request that the local virtual server send any e-mail messages that it has in the queue for the domains indicated in the ETRN command.


Allows a remote host and the local host to switch roles and send mail in the reverse direction, without establishing a new connection.

For more information about how to restore the default support for these verbs, see Microsoft Knowledge Base article 257569 "How to turn off ESMTP verbs in Exchange 2000 Server and in Exchange Server 2003" (