yahoo2mbox: 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/yahoo2mbox - from package: yahoo2mbox

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

Error in other languages:
yahoo2mbox: bevel nie gevind nie
yahoo2mbox: comandă negăsită
yahoo2mbox: comando não encontrado
yahoo2mbox: commande introuvable
yahoo2mbox: command not found
yahoo2mbox: käsku ei ole
yahoo2mbox: không tìm thấy lệnh
yahoo2mbox: komanda nerasta
yahoo2mbox: Kommando nicht gefunden.
yahoo2mbox: kommandot finns inte
yahoo2mbox: komut yok
yahoo2mbox: nie znaleziono polecenia
yahoo2mbox: níor aimsíodh an t-ordú
yahoo2mbox: no se encontró la orden
yahoo2mbox: no s'ha trobat l'ordre
yahoo2mbox: opdracht niet gevonden
yahoo2mbox: parancs nem található
yahoo2mbox: perintah tidak ditemukan
yahoo2mbox: príkaz nenájdený
yahoo2mbox: příkaz nenalezen
yahoo2mbox: команда не найдена
yahoo2mbox: командата не е открита
yahoo2mbox: 命令找不到
yahoo2mbox: コマンドが見つかりません