If you’re a Virtualmin user and use the iptables based firewall, you may have issues with outbound FTP working. The FTP connection can often be made, but then stalls at receiving data.
You can fix this by adding the nf_conntrack_ftp module to your machine. As root or sudo bash, create the following file:
and within that file put:
This will make sure that module gets loaded after each boot and fix your connection issue.