This message is returned to the mail client from the local host when the mail server has detected an SMTP command that it does not support. Support for the SMTP command might be disallowed because of SMTP configuration settings.
See the z/OS Communications Server: IP Configuration Reference for more information about the DISALLOWCMD configuration statement.
smtp_command is the name of the command that was not implemented
SMTP continues.
Notify the owner of the remote SMTP client and the local SMTP server of the problem.
Check the SMTP configuration file on the local server for the DISALLOWCMD. If it is not correct, modify it and restart SMTP.