clamassassin: 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/clamassassin - from package: clamassassin

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

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