Port range should not be ignored anymore.
Please note that setting a port range to a client object (Rebex.Net.Ftp) affects port selection of the client (local end) only, not the server (remote end). Therefore remote end can have address such 46.4.51.132:61265.
To understand what is going on, I will shortly describe how the FTP protocol works:
By default, client connects from random address:port e.g. 172.26.5.207:3225 to the FTP server's address on port 21 (for plain FTP) or port 990 (for implicit FTP/SSL) e.g. 46.4.51.132:990. Of course ports can be often configured at server side.
When the client wants to upload or download a file, it requests a data connection. It can be done by two ways: passive or active.
In passive mode, the client sends the command PASV and server replies with "connect to address:port" - the remote port is selected randomly (often port range can be configured at server) e.g. 46.4.51.132:61265.
Then client connects to the specified address:port, the local port is selected randomly (if a port range is specified, the local port is selected from this port range) e.g. 172.26.5.207:42900
In active mode, the client sends the command "PORT address:port", the (local) port is selected randomly (from port range if specified) e.g. "PORT 172.26.5.207:42900".
Then the server connects to the client to specified address:port from it's address and random (remote) port e.g. 46.4.51.132:61265.
Because you received Rebex.Net.FtpException: Illegal PORT command (500). It means that your server doesn't support active mode.
To use data port range on client, your code should start like this:
Ftp ftp = new Ftp();
ftp.Connect("46.4.51.132", SslMode.Implicit);
ftp.Login(user, password);
ftp.DataPortRange = new PortRange(42900, 49250);
Please, try the suggestion above and leave me a comment if your local ports are still outside the specified port range. To restrict remote ports you have to configure your FTP server.