copy - paste : duplicate files on server

Hi guys !
when I copy-paste a folder ON THE SERVER, this folder is moved instead of duplicated (As if I had done cut-paste).
Does anyone know the problem ?
Is SmartFTP smart enough to duplicate folders on the server, without download and upload through my computer ?
Does the problem come from the server or from SmartFTP ?
If it comes from the server, what is the pb ?
is there anyone who ever try (and succeed) to DUPLICATE files directly on the server ?
(excuse my french english)

EDIT: I just tried to copy a file on a server by opening two connections to it and FXP'ing the file, and it worked :-)

Unfortunately, my server doesn't seem to support FXP : Here is the error messagge I got when I tried to do a FXP transfer between the server and itself :
500 Illegal EPRT command.
Echec du transfert

Try to connect via IPv4 instead of IPv6.

Try to connect via IPv4 instead of IPv6.
That's what I did ( parameters indicate IPv4).
I 'm going to contact the support to know if FXP is possible on my server.

I 'll write the answer here later.

Thank you.

IPv4 or IPv6 has no influence.

The EPRT and EPSV commands are choosen because most NAT routers do not translate them. This is necessary for FXP transfers. If these commands are not announced in the FEAT reply they won't be used. The problem here is that your server - as most other servers - do not allow FXP transfers.