sa-heatu: 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 Debian possible default full paths are:

/usr/bin/sa-heatu - from package: spamassassin-heatu

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

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