telnet-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/telnet-ssl - from package: telnet-ssl

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

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