Assume that I have a project named user_registration and it contains an app named accounts.

At first, we need to configure our email server. So, got to user_registration/setting.py and write the follwoing lines:

EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'  
MAILER_EMAIL_BACKEND = EMAIL_BACKEND  
EMAIL_HOST = 'your_mail_server'  
EMAIL_HOST_PASSWORD = 'your_password'  
EMAIL_HOST_USER = 'your_email'  
EMAIL_PORT = 465  
EMAIL_USE_SSL = True  
DEFAULT_FROM_EMAIL = EMAIL_HOST_USER

To test above configuration work, open up the terminal and navigate to user_registration project and run following command:

$ python manage.py shell
>>> from django.core.mail import send_mail
>>> send_mail( 'Subject here', 'Here is the message.', 'me@shafikshaon.com', ['shafikshaon@gmail.com'], fail_silently=False, )

It will return 1 as status code. Then check your mail, a mail will arrive.

Now create a form in accounts/templates/accounts/signup.html and write the following code:

<!DOCTYPE html>  
<html lang="en">  
<head>  
    <title>Signup</title>  
    <meta charset="utf-8">  
    <meta name="viewport" content="width=device-width, initial-scale=1">  
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">  
</head>  
<body>  

<div class="container" style="margin-top: 50px;">  
    <div class="row justify-content-center">  
        <div class="col-md-5 shadow-sm p-3 mb-5 bg-white rounded">  
            <h2>Signup</h2>  
            <form method="post">  
                {% csrf_token %}  
                <div class="form-group">  
                    <label for="first_name">First Name:</label>  
                    <input type="text" class="form-control" id="first_name" placeholder="Enter first name"  
  name="first_name">  
                </div>  
                <div class="form-group">  
                    <label for="last_name">Last Name:</label>  
                    <input type="text" class="form-control" id="last_name" placeholder="Enter last name"  
  name="last_name">  
                </div>  
                <div class="form-group">  
                    <label for="username">Username:</label>  
                    <input type="text" class="form-control" id="username" placeholder="Enter username" name="username">  
                </div>  
                <div class="form-group">  
                    <label for="email">Email:</label>  
                    <input type="email" class="form-control" id="email" placeholder="Enter email" name="email">  
                </div>  
                <div class="form-group">  
                    <label for="pwd1">Password:</label>  
                    <input type="password" class="form-control" id="pwd1" placeholder="Enter password" name="password1">  
                </div>  
                <div class="form-group">  
                    <label for="pwd2">Confirm Password:</label>  
                    <input type="password" class="form-control" id="pwd2" placeholder="Reenter password"  
  name="password2">  
                </div>  
                <button type="submit" class="btn btn-primary">Submit</button>  
            </form>  
        </div>  
    </div>  
</div>  

</body>  
</html>

Now create a form in accounts/templates/accounts/acc_active_email.html and write the following code:

{% autoescape off %}  
Hi {{ user.username }},  
Please click on the link to confirm your registration,  

http://{{ domain }}{% url 'activate' uidb64=uid token=token %}  
If you think, it's not you, then just ignore this email.  
{% endautoescape %}

Now open up accounts/urls.py and write the following path:

from django.urls import path  
from accounts import views  

urlpatterns = [  
    path('signup/', views.signup, name="signup"),  
    path('activate/<uidb64>/<token>/',views.activate, name='activate'),  
]

Now open up accounts/tokens.py and write the following code:

from django.contrib.auth.tokens import PasswordResetTokenGenerator  
from django.utils import six  


class AccountActivationTokenGenerator(PasswordResetTokenGenerator):  
    def _make_hash_value(self, user, timestamp):  
        return (  
            six.text_type(user.pk) + six.text_type(timestamp) +  
            six.text_type(user.is_active)  
        )  

account_activation_token = AccountActivationTokenGenerator()

Now open up accounts/forms.py and write the following code:

from django.contrib.auth.forms import UserCreationForm  
from django.contrib.auth.models import User  


class SignUpForm(UserCreationForm):  
    class Meta:  
        model = User  
        fields = ('email', 'first_name', 'last_name', 'username')

Now open up accounts/views.py and write the following code:

from django.http import HttpResponse  
from django.shortcuts import render  
from django.contrib.sites.shortcuts import get_current_site  
from django.utils.encoding import force_bytes, force_text  
from django.utils.http import urlsafe_base64_encode, urlsafe_base64_decode  
from django.template.loader import render_to_string  

from .forms import SignUpForm  
from .tokens import account_activation_token  
from django.contrib.auth.models import User  
from django.core.mail import EmailMessage  


def signup(request):  
    if request.method == 'GET':  
        return render(request, 'accounts/signup.html')  
    if request.method == 'POST':  
        form = SignUpForm(request.POST)  
        # print(form.errors.as_data())  
        if form.is_valid():  
            user = form.save(commit=False)  
            user.is_active = False  
            user.save()  
            current_site = get_current_site(request)  
            mail_subject = 'Activate your account.'  
            message = render_to_string('accounts/acc_active_email.html', {  
                'user': user,  
                'domain': current_site.domain,  
                'uid': urlsafe_base64_encode(force_bytes(user.id)).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 HttpResponse('Please confirm your email address to complete the registration')  
     else:  
        form = SignUpForm()  
     return render(request, 'accounts/signup.html', {'form': form})  


def activate(request, uidb64, token):  
    try:  
        uid = force_text(urlsafe_base64_decode(uidb64))  
        user = User.objects.get(id=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  
        user.save()  
        return HttpResponse('Thank you for your email confirmation. Now you can login your account.')  
    else:  
        return HttpResponse('Activation link is invalid!')

When user signup, is_active set to False that means user set to inactive during signup process. By render_to_string() method which data/ value send over conext. Here, data/ value send overaccounts/acc_active_email.html and user, domain, uid, and token data as context data.

Convert uid into text. Then, find user object by uid. Now check account_activation_token.check_token(user, token) to check is this match with previously creaed token. If match the user.is_active set to True.