As a far as i am aware of, you have to use your prefere scp api to upload the file to your ftp server. because JBossESB does not provide anything like outgoing gateway to outpout your message to let say an ftp server directory. Some body may tell you to use the notify action but this is really not a solution. so you have to write an action to capture the bytestream of your message and use the scp api to write to the remote ftp server.
If you find a better solution i would be glad to know about it as i have the same requirement.