ftp-ssl: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/ftp-ssl - from package: ftp-ssl

You may install the required package with command apt-get install {package}

Error in other languages:
ftp-ssl: bevel nie gevind nie
ftp-ssl: comandă negăsită
ftp-ssl: comando não encontrado
ftp-ssl: commande introuvable
ftp-ssl: command not found
ftp-ssl: käsku ei ole
ftp-ssl: không tìm thấy lệnh
ftp-ssl: komanda nerasta
ftp-ssl: Kommando nicht gefunden.
ftp-ssl: kommandot finns inte
ftp-ssl: komut yok
ftp-ssl: nie znaleziono polecenia
ftp-ssl: níor aimsíodh an t-ordú
ftp-ssl: no se encontró la orden
ftp-ssl: no s'ha trobat l'ordre
ftp-ssl: opdracht niet gevonden
ftp-ssl: parancs nem található
ftp-ssl: perintah tidak ditemukan
ftp-ssl: príkaz nenájdený
ftp-ssl: příkaz nenalezen
ftp-ssl: команда не найдена
ftp-ssl: командата не е открита
ftp-ssl: 命令找不到
ftp-ssl: コマンドが見つかりません