Django success url

Прописываю в success_url путь success_url = 'main/index.html'

Однако выдает ошибку, что путь не найден:

Page not found (404)
Request Method: GET
Request URL:    http://127.0.0.1:8000/main/index.html
Using the URLconf defined in caparol_center_spb_decision.urls, Django tried these URL patterns, in this order:

admin/
[name='index']
decision/
The current path, main/index.html, didn't match any of these.

Хотя он есть в папке templates/main/index.html

views:

class ContactView(FormView):
    template_name = 'main/index.html'
    form_class = EmailForm
    success_url = 'main/index.html'
    success_message = "Письмо успешно отправлено"

    def form_valid(self, form):
        email = form.cleaned_data['email']
        send_mail('Caparol_Center_Spb',
                  'Теперь вы будете получать лучшие предложения шоу-рума',
                  email,
                  [email, ],
                  fail_silently=False,)
        return super().form_valid(form)

    def form_invalid(self, form):
        return HttpResponse('Unsuccess')

urls:

from django.urls import path
from .views import ContactView

app_name = 'main'

urlpatterns = [
    path('', ContactView.as_view(), name='index')
]