How to manage users that put wrong email in registration but saved in the database

I write some code to register a user. In my fonction "register(request)", Before i do email verification i save the user and he is saved in the database but he is not active. Then i use this user to activate him in my function "activate(request)" and i activate the user. But there is a problem, if the user put a wrong or not email, he will be saved in database, and this can take useless memory space in database. And the other problem is that if the user want to correct his informations on registration page, he will not be able to do that because his username and email already exists in database.

def register(request):
    registered = False
    if request.method == 'POST':
        form = UserForm(data=request.POST)
        if form.is_valid():
            user = form.save(commit=False)
            user.is_active = False
            user.save()
            current_site = get_current_site(request)
            mail_subject = 'Activez votre compte acquisitor.'
            message = render_to_string('users/acc_active_email.html',{
                'user': user,
                'domain': current_site.domain,
                'uid': urlsafe_base64_encode(force_bytes(user.pk)).decode(),
                'token': account_activation_token.make_token(user),
            })
            to_email = form.cleaned_data.get('email')
            email = EmailMessage(
                mail_subject, message, to=[to_email]
            )
            email.send()
            return render(request, 'users/mail_registration.html')
        else:
            print(form.errors)
    else:
        form = UserForm()
    return render(request, 'users/registration.html', {'user_form': form,
                                                'registered': registered})


def activate(request, uidb64, token, backend='django.contrib.auth.backends.ModelBackend'):
    try:
        uid = force_text(urlsafe_base64_decode(uidb64))
        user = User.objects.get(pk=uid)
    except(TypeError, ValueError, OverflowError, User.DoesNotExist):
        user = None
    if user is not None and account_activation_token.check_token(user, token):
        user.is_active = True
        registered = True
        user.save()
        login(request, user, backend)
        return HttpResponseRedirect(reverse('index'))
    else:
        return HttpResponse("Lien d'activation invalide")