Help needed - spam bot is producing thousands of error mails

Hello,
need help and advice. Since yesterday some spam bot is attacking a client’s website where I use Formloom4 for inscription to courses.
I know that the CSRF is exactly there for preventing spam and it is working. Thanks @yabdab
But it is still annoying to receive thousands of the error mails and to know that some idiot is attacking a NGO website.
On the main page there is no Formloom-form.
I renamed and redirected the site with the Formloom form.
Anyone can assist in stopping this?
Host is Strato.
Tia,
Tom