kbxutil: 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/kbxutil - from package: gnupg2-smime

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

On Debian possible default full paths are:

/usr/bin/kbxutil - from package: gnupg2

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

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