itip: 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/itip - from package: vpim

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

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