exiqsumm: 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/sbin/exiqsumm - from package: exim

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

On Debian possible default full paths are:

/usr/sbin/exiqsumm - from package: exim4-base

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

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