nag-import-openxchange: 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/nag-import-openxchange - from package: php-horde-nag

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

On Debian possible default full paths are:

/usr/bin/nag-import-openxchange - from package: php-horde-nag

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

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