webmlmd: command not found

Have You tried accessing the binary with the full path?

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/webmlmd - from package: courier-mlm

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