maildirsync: 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/maildirsync - from package: maildirsync

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

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