500 FTP Reply Code - KB Article #1525Related Articles --
500 Syntax error, command unrecognized.
A 500 reply code may be sent in response to any command that the server is unable to recognize. It is a permanent negative reply, which means the client is discouraged from sending the command again since the server will respond with the same reply code. It usually means that the client has sent a command to the server that the server does not recognize. This may be due to an error in the spelling or formatting of the command itself or that the command is newer than the FTP implementation in place on the server or is a proprietary command of another server implementation.
A 500 reply code may be sent in response to any FTP command.