smd-client: 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-client - from package: syncmaildir

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

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