datemail: 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/datemail - from package: qmail
/var/lib/qmail/bin/datemail - from package: qmail

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

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