If you run a firewall on your Linux server and want to use passive FTP connections, you have to define the passive port range in pure-ftpd and your firewall to ensure that the connections dont get blocked. The following example is for pure-ftpd on Debian or Ubuntu Linux and ISPConfig 3:
1) Configure pure-ftpd
echo "40110 40210" > /etc/pure-ftpd/conf/PassivePortRange /etc/init.d/pure-ftpd-mysql restart
2) Configure the firewall. If you use ISPConfig 3 on my server to configure the bastille firewall, you can add the nescessera port range in the ISPConfig firewall settings.
Change the list of Open TCP ports from:
and then click on "Save".