FTP HELP . ORG
If you are using windows Internet Explorer (not Mac IE, since that doesn't have full FTP support) for FTP, then you can enable it using the following:
-To do this in Internet Explorer for Windows, open Internet Explorer, click Tools, then Internet Options. Click the Advanced tab. Then scroll down until you find an option similar to "Enable Passive Transfers for FTP". Check the box, click Apply, then Ok. You may need to restart Internet Explorer.
Advanced FTP Resources
(Programming, RFC, protocol info)
Internet Explorer as an FTP client
Free FTP clients
FTP FAQ
Otherwise, with other FTP software, there should be an option for PASV (or Passive Mode) that is a checkbox. Often, it is in the same information screen that the customer types their log-in info into.
Ask the client to look for an option that is called "Passive Mode", or "PASV Mode" in their software. Ensure it is enabled.
FTP related RFC's
Sometimes, configuring the FTP software can get tricky. Here is a simple guide for getting connected.
a. There are 3 things you need to know to get connected with FTP:
1) The Internet address of the FTP server you wish to connect to. This is often similar-looking to a website, but without the "http://". For example, it might be "ftp.mycompany.com" or "thisplace.org". It also might be a numeric IP address, like 216.238.107.66.
Connecting to an FTP server
Turning on Passive mode
(this helps connecting under most circumstances)