Life of an Admin

After trying everything, giving all permissions, trying different ftp servers, on windows and on linux, if you can connect and read but still cant do uploads on external ftp server, then you better check your ftp rule in ISA. By default the ISA protocol has uploads denied in the ftp filter. So whenever you create ftp access rule, make sure you enable uploads specifically (if you need it) otherwise it will be blocked.

1. In the console tree of ISA Server Management, click Firewall Policy.
2. In the details pane, click a server publishing rule or access rule that applies to FTP traffic.
3. On the Tasks tab, click Edit Selected Rule.
4. On the Traffic tab (for a server publishing rule) or on the Protocols tab (for an access rule), click Filtering, and then click Configure FTP.
5. On the Protocol tab, select Read Only, if FTP uploads should be blocked.

HTH