Django Comments XTD EMail notifications

models.py

from django.core.mail import send_mail
from django.db import models
from django.dispatch import receiver
from django_comments_xtd.models import XtdComment

class CommentMailFilter(models.Model):
    # To prevent duplicate mails
    id = models.IntegerField(primary_key=True)

def _comment2html(comment: XtdComment, with_header=True):
    response = ""
    if with_header:
        url = comment.get_content_object_url()
        response += f"<a href='{url}'>View page</a><hr/>"

    response += f"<p><b>{comment.user or comment.name}</b> wrote:</p>"
    response += f"<blockquote>{comment.comment}</blockquote>"
    if comment.parent_id != comment.id:
        parent = XtdComment.objects.get(id=comment.parent_id)
        response += f"<p>at {comment.submit_date}, reply to:</p>"
        response += _comment2html(parent, with_header=False)
    else:
        response += f"<p>at {comment.submit_date}</p>"

    return response


@receiver(models.signals.post_save)
def comment_to_email(instance: XtdComment, **kwargs):
    if not isinstance(instance, XtdComment):
        return
    if not instance.is_public or instance.is_removed:
        return          # Don't send hidden comments
    if instance.user and instance.user.groups.filter(name="Editors").exists():
        return          # Don't send editor's comments
    if CommentMailFilter.objects.filter(id=instance.id).exists():
        return

    # Prevent duplicate mail send
    CommentMailFilter(id=instance.id).save()

    user_name = instance.user or instance.name
    send_mail(f"{user_name} commented on {instance.site.domain}",
              instance.get_as_text(),
              "comments@melianmiko.ru",
              ["admin@melianmiko.ru"],
              html_message=_comment2html(instance),
              fail_silently=False)