mailsound: 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/mailsound - from package: rplay-contrib

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

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