Problem using Curl for FTP upload
I have an issue on one of the sites I manage when trying to connect out to an external FTP server. From a client on the network I am using Curl to process FTP uploads. I can connect to the FTP server manually using FileZilla and upload files successfully. However, when trying to use Curl it will not work without the argument "--disable-epsv" specified. This forces the connection into Extended Passive mode.
I assume there is something on my firewall blocking this connection but I cannot figure out what. Any help would be greatly appreciated.