getmail: 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/getmail - from package: getmail

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

On Debian possible default full paths are:

/usr/bin/getmail - from package: getmail4

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

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