posttls-finger: 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/sbin/posttls-finger - from package: postfix

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

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