Topic Last Modified: 2006-08-21

The Microsoft® Exchange Server Analyzer Tool transmits the EHLO Extended Simple Mail Transfer Protocol (ESMTP) command verb to port 25 of a remote server and analyzes the response to determine whether the remote server supports the BDAT ESMTP verb.

If the response received from the remote server in reply to the BDAT command verb does not indicate a non-retrievable error, the Exchange Server Analyzer then transmits a test message to the remote server and analyzes the response to determine whether the message transfer was successful.

If the Exchange Server Analyzer does not receive the expected response string of '250', the Exchange Server Analyzer displays an error.

Exchange Server 2003 uses Exchange-specific extended SMTP verbs to communicate with other servers that run Exchange Server in the organization. It is more efficient to communicate with Exchange-specific extended SMTP verbs than by using standard SMTP. If support for the ESMTP command set is disabled, Exchange Server performance may be hindered.

The BDAT ESMTP command verb is an alternative to the DATA command. 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. This takes two arguments:

This error indicates that although the BDAT ESMTP command verb is supported by the remote server, the subsequent BDAT mail acceptance test failed.

To resolve this error, check the messaging environment for issues or configurations that might be blocking the BDAT command verb such as:

For more information about how to remove or 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" (

For more information about how Exchange Server uses the ESMTP command verbs, see "How to Load Exchange SMTP Properly" in the Exchange Server Transport and Routing Guide (