wmail: 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/wmail - from package: wmail

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

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