proofserv.exe: 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 CentOS possible default full paths are:

/usr/bin/proofserv.exe - from package: root-proofd

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/proofserv.exe - from package: root-system-proofd

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

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