smtpdcheck: 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/smtpdcheck - from package: mailavenger

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

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