proofserv: 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 - 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 - from package: root-system-proofd

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

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