500 SITE my.com is an unknown extension

I'm a newbie and can't find an answer to this anwhere in posts or all the other wonderful resources. Have been trying to connect with a new installation of Smart FTP - It goes like this

SmartFTP v1.0.982.36
Resolving host name jensclassroom.com...
Resolving host name jensclassroom.com...
Connecting to Proxy (jensclassroom.com) -> IP: Connected to Proxy (jensclassroom.com) -> Time = 20ms
Socket connected waiting for login sequence.
220---------- Welcome to Pure-FTPd [TLS] ----------
220-You are user number 3 of 50 allowed.
220-Local time is now 07:35. Server port: 21.
220-This is a private system - No anonymous login
220 You will be disconnected after 15 minutes of inactivity.
USER jensclas
331 User jensclas OK. Password required
PASS (hidden)
230-User jensclas has group access to: jensclas
230-This server supports FXP transfers
230 OK. Current restricted directory is /
SITE jensclassroom.com
500 SITE jensclassroom.com is an unknown extension
Cannot login waiting to retry (30s)...
Continue to login attempt 2...


and on it goes..so what does

500 SITE jensclassroom.com is an unknown extension

mean and how do I fix it???

Thanks

The SITE command is commonly used by the FTP server administrator as a way to configure the server settings using an FTP client. Different FTP servers support different parameters to this command. These commands usually look something like "SITE ADDUSER group user", which allows the administrator to add a new FTP user. I can't imagine what "SITE jensclassroom.com" should do or why it's even send to the server.