smd-check-conf: 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/smd-check-conf - from package: syncmaildir

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

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