exim_dumpdb: 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/exim_dumpdb - from package: exim

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

On Debian possible default full paths are:

/usr/sbin/exim_dumpdb - from package: exim4-base
/usr/lib/debug/usr/sbin/exim_dumpdb - from package: exim4-dbg

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

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