Many organizations use firewalls that act as intercepting proxies to external servers. You should be able to access an external FTP server the same way that you access an internal server.
FTP without encryption is usually not recommended as it sends usernames, passwords and data over the Internet unencryped. Some people use PGP to encrypt the data before sending it. Some people use secure FTP.
I have a real example you can reference to see how to use EXPECT commands within HCITCL to automate an interactive SSH/SFTP session at the following URL:
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