rspamc: 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/rspamc - from package: rspamd

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

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