exim_fixdb: 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_fixdb - from package: exim

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

On Debian possible default full paths are:

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

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

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