The Flask Mega-Tutorial Part X: Email Support

This is the tenth installment of the Flask Mega-Tutorial series, in which I'm going to tell you how your application can send emails to your users, and how to build a password recovery feature on top of the email support.

For your reference, below is a list of the articles in this series.

Note 1: If you are looking for the legacy version of this tutorial, it's here.

Note 2: If you would like to support my work on this blog, or just don't have patience to wait for weekly articles, I am offering the complete version of this tutorial packaged as an ebook or a set of videos. For more information, visit courses.miguelgrinberg.com.

The application is doing pretty well on the database front now, so in this chapter I want to depart from that topic and add another important piece that most web applications need, which is the sending of emails.

Why does an application need to email its users? There are many reasons, but one common one is to solve authentication related problems. In this chapter I'm going to add a password reset feature for users that forget their password. When a user requests a password reset, the application will send an email with a specially crafted link. The user then needs to click that link to have access to a form in which to set a new password.

The GitHub links for this chapter are: Browse, Zip, Diff.

Introduction to Flask-Mail

As far as the actual sending of emails, Flask has a popular extension called Flask-Mail that can make the task very easy. As always, this extension is installed with pip:

(venv) $ pip install flask-mail

The password reset links will have a secure token in them. To generate these tokens, I'm going to use JSON Web Tokens, which also have a popular Python package:

(venv) $ pip install pyjwt

The Flask-Mail extension is configured from the app.config object. Remember when in Chapter 7 I added the email configuration for sending yourself an email whenever an error occurred in production? I did not tell you this then, but my choice of configuration variables was modeled after Flask-Mail's requirements, so there isn't really any additional work that is needed, the configuration variables are already in the application.

Like most Flask extensions, you need to create an instance right after the Flask application is created. In this case this is an object of class Mail:

app/__init__.py: Flask-Mail instance.

# ...
from flask_mail import Mail

app = Flask(__name__)
# ...
mail = Mail(app)

If you are planning to test sending of emails you have the same two options I mentioned in Chapter 7. If you want to use an emulated email server, Python provides one that is very handy that you can start in a second terminal with the following command:

(venv) $ python -m smtpd -n -c DebuggingServer localhost:8025

To configure for this server you will need to set two environment variables:

(venv) $ export MAIL_SERVER=localhost
(venv) $ export MAIL_PORT=8025

If you prefer to have emails sent for real, you need to use a real email server. If you have one, then you just need to set the MAIL_SERVER, MAIL_PORT, MAIL_USE_TLS, MAIL_USERNAME and MAIL_PASSWORD environment variables for it. If you want a quick solution, you can use a Gmail account to send email, with the following settings:

(venv) $ export MAIL_SERVER=smtp.googlemail.com
(venv) $ export MAIL_PORT=587
(venv) $ export MAIL_USE_TLS=1
(venv) $ export MAIL_USERNAME=<your-gmail-username>
(venv) $ export MAIL_PASSWORD=<your-gmail-password>

If you are using Microsoft Windows, you need to replace export with set in each of the export statements above.

Remember that the security features in your Gmail account may prevent the application from sending emails through it unless you explicitly allow "less secure apps" access to your Gmail account. You can read about this here, and if you are concerned about the security of your account, you can create a secondary account that you configure just for testing emails, or you can enable less secure apps only temporarily to run your tests and then revert back to the more secure default.

Flask-Mail Usage

To learn how Flask-Mail works, I'll show you how to send an email from a Python shell. So fire up Python with flask shell, and then run the following commands:

>>> from flask_mail import Message
>>> from app import mail
>>> msg = Message('test subject', sender=app.config['ADMINS'][0],
... recipients=['your-email@example.com'])
>>> msg.body = 'text body'
>>> msg.html = '<h1>HTML body</h1>'
>>> mail.send(msg)

The snippet of code above will send an email to a list of email addresses that you put in the recipients argument. I put the sender as the first configured admin (I've added the ADMINS configuration variable in Chapter 7). The email will have plain text and HTML versions, so depending on how your email client is configured you may see one or the other.

So as you see, this is pretty simple. Now let's integrate emails into the application.

A Simple Email Framework

I will begin by writing a helper function that sends an email, which is basically a generic version of the shell exercise from the previous section. I will put this function in a new module called app/email.py:

app/email.py: Email sending wrapper function.

from flask_mail import Message
from app import mail

def send_email(subject, sender, recipients, text_body, html_body):
    msg = Message(subject, sender=sender, recipients=recipients)
    msg.body = text_body
    msg.html = html_body

Flask-Mail supports some features that I'm not utilizing here such as Cc and Bcc lists. Be sure to check the Flask-Mail Documentation if you are interested in those options.

Requesting a Password Reset

As I mentioned above, I want users to have the option to request their password to be reset. For this purpose I'm going to add a link in the login page:

app/templates/login.html: Password reset link in login form.

        Forgot Your Password?
        <a href="{{ url_for('reset_password_request') }}">Click to Reset It</a>

When the user clicks the link, a new web form will appear that requests the user's email address as a way to initiate the password reset process. Here is the form class:

app/forms.py: Reset password request form.

class ResetPasswordRequestForm(FlaskForm):
    email = StringField('Email', validators=[DataRequired(), Email()])
    submit = SubmitField('Request Password Reset')

And here is the corresponding HTML template:

app/templates/reset_password_request.html: Reset password request template.

{% extends "base.html" %}

{% block content %}
    <h1>Reset Password</h1>
    <form action="" method="post">
        {{ form.hidden_tag() }}
            {{ form.email.label }}<br>
            {{ form.email(size=64) }}<br>
            {% for error in form.email.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
        <p>{{ form.submit() }}</p>
{% endblock %}

I also need a view function to handle this form:

app/routes.py: Reset password request view function.

from app.forms import ResetPasswordRequestForm
from app.email import send_password_reset_email

@app.route('/reset_password_request', methods=['GET', 'POST'])
def reset_password_request():
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    form = ResetPasswordRequestForm()
    if form.validate_on_submit():
        user = User.query.filter_by(email=form.email.data).first()
        if user:
        flash('Check your email for the instructions to reset your password')
        return redirect(url_for('login'))
    return render_template('reset_password_request.html',
                           title='Reset Password', form=form)

This view function is fairly similar to others that process a form. I start by making sure the user is not logged in. If the user is logged in, then there is no point in using the password reset functionality, so I redirect to the index page.

When the form is submitted and valid, I look up the user by the email provided by the user in the form. If I find the user, I send a password reset email. I'm using a send_password_reset_email() helper function to do this. I will show you this function below.

After the email is sent, I flash a message directing the user to look for the email for further instructions, and then redirect back to the login page. You may notice that the flashed message is displayed even if the email provided by the user is unknown. This is so that clients cannot use this form to figure out if a given user is a member or not.

Password Reset Tokens

Before I implement the send_password_reset_email() function, I need to have a way to generate a password request link. This is going to be the link that is sent to the user via email. When the link is clicked, a page where a new password can be set is presented to the user. The tricky part of this plan is to make sure that only valid reset links can be used to reset an account's password.

The links are going to be provisioned with a token, and this token will be validated before allowing the password change, as proof that the user that requested the email has access to the email address on the account. A very popular token standard for this type of process is the JSON Web Token, or JWT. The nice thing about JWTs is that they are self contained. You can send a token to a user in an email, and when the user clicks the link that feeds the token back into the application, it can be verified on its own.

How do JWTs work? Nothing better than a quick Python shell session to understand them:

>>> import jwt
>>> token = jwt.encode({'a': 'b'}, 'my-secret', algorithm='HS256')
>>> token
>>> jwt.decode(token, 'my-secret', algorithms=['HS256'])
{'a': 'b'}

The {'a': 'b'} dictionary is an example payload that is going to be written into the token. To make the token secure, a secret key needs to be provided to be used in creating a cryptographic signature. For this example I have used the string 'my-secret', but with the application I'm going to use the SECRET_KEY from the configuration. The algorithm argument specifies how the token is to be generated. The HS256 algorithm is the most widely used.

As you can see the resulting token is a long sequence of characters. But do not think that this is an encrypted token. The contents of the token, including the payload, can be decoded easily by anyone (don't believe me? Copy the above token and then enter it in the JWT debugger to see its contents). What makes the token secure is that the payload is signed. If somebody tried to forge or tamper with the payload in a token, then the signature would be invalidated, and to generate a new signature the secret key is needed. When a token is verified, the contents of the payload are decoded and returned back to the caller. If the token's signature was validated, then the payload can be trusted as authentic.

The payload that I'm going to use for the password reset tokens is going to have the format {'reset_password': user_id, 'exp': token_expiration}. The exp field is standard for JWTs and if present it indicates an expiration time for the token. If a token has a valid signature, but it is past its expiration timestamp, then it will also be considered invalid. For the password reset feature, I'm going to give these tokens 10 minutes of life.

When the user clicks on the emailed link, the token is going to be sent back to the application as part of the URL, and the first thing the view function that handles this URL will do is to verify it. If the signature is valid, then the user can be identified by the ID stored in the payload. Once the user's identity is known, the application can ask for a new password and set it on the user's account.

Since these tokens belong to users, I'm going to write the token generation and verification functions as methods in the User model:

app/models.py: Reset password token methods.

from time import time
import jwt
from app import app

class User(UserMixin, db.Model):
    # ...

    def get_reset_password_token(self, expires_in=600):
        return jwt.encode(
            {'reset_password': self.id, 'exp': time() + expires_in},
            app.config['SECRET_KEY'], algorithm='HS256')

    def verify_reset_password_token(token):
            id = jwt.decode(token, app.config['SECRET_KEY'],
        return User.query.get(id)

The get_reset_password_token() function returns a JWT token as a string, which is generated directly by the jwt.encode() function.

The verify_reset_password_token() is a static method, which means that it can be invoked directly from the class. A static method is similar to a class method, with the only difference that static methods do not receive the class as a first argument. This method takes a token and attempts to decode it by invoking PyJWT's jwt.decode() function. If the token cannot be validated or is expired, an exception will be raised, and in that case I catch it to prevent the error, and then return None to the caller. If the token is valid, then the value of the reset_password key from the token's payload is the ID of the user, so I can load the user and return it.

Sending a Password Reset Email

Now that I have the tokens, I can generate the password reset emails. The send_password_reset_email() function relies on the send_email() function I wrote above.

app/email.py: Send password reset email function.

from flask import render_template
from app import app

# ...

def send_password_reset_email(user):
    token = user.get_reset_password_token()
    send_email('[Microblog] Reset Your Password',
                                         user=user, token=token),
                                         user=user, token=token))

The interesting part in this function is that the text and HTML content for the emails is generated from templates using the familiar render_template() function. The templates receive the user and the token as arguments, so that a personalized email message can be generated. Here is the text template for the reset password email:

app/templates/email/reset_password.txt: Text for password reset email.

Dear {{ user.username }},

To reset your password click on the following link:

{{ url_for('reset_password', token=token, _external=True) }}

If you have not requested a password reset simply ignore this message.


The Microblog Team

And here is the nicer HTML version of the same email:

app/templates/email/reset_password.html: HTML for password reset email.

<p>Dear {{ user.username }},</p>
    To reset your password
    <a href="{{ url_for('reset_password', token=token, _external=True) }}">
        click here
<p>Alternatively, you can paste the following link in your browser's address bar:</p>
<p>{{ url_for('reset_password', token=token, _external=True) }}</p>
<p>If you have not requested a password reset simply ignore this message.</p>
<p>The Microblog Team</p>

The reset_password route that is referenced in the url_for() call in these two email templates does not exist yet, this will be added in the next section. The _external=True argument that I included in the url_for() calls in both templates is also new. The URLs that are generated by url_for() by default are relative URLs, so for example, the url_for('user', username='susan') call would return /user/susan. This is normally sufficient for links that are generated in web pages, because the web browser takes the remaining parts of the URL from the current page. When sending a URL by email however, that context does not exist, so fully qualified URLs need to be used. When _external=True is passed as an argument, complete URLs are generated, so the previous example would return http://localhost:5000/user/susan, or the appropriate URL when the application is deployed on a domain name.

Resetting a User Password

When the user clicks on the email link, a second route associated with this feature is triggered. Here is the password request view function:

app/routes.py: Password reset view function.

from app.forms import ResetPasswordForm

@app.route('/reset_password/<token>', methods=['GET', 'POST'])
def reset_password(token):
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    user = User.verify_reset_password_token(token)
    if not user:
        return redirect(url_for('index'))
    form = ResetPasswordForm()
    if form.validate_on_submit():
        flash('Your password has been reset.')
        return redirect(url_for('login'))
    return render_template('reset_password.html', form=form)

In this view function I first make sure the user is not logged in, and then I determine who the user is by invoking the token verification method in the User class. This method returns the user if the token is valid, or None if not. If the token is invalid I redirect to the home page.

If the token is valid, then I present the user with a second form, in which the new password is requested. This form is processed in a way similar to previous forms, and as a result of a valid form submission, I invoke the set_password() method of User to change the password, and then redirect to the login page, where the user can now login.

Here is the ResetPasswordForm class:

app/forms.py: Password reset form.

class ResetPasswordForm(FlaskForm):
    password = PasswordField('Password', validators=[DataRequired()])
    password2 = PasswordField(
        'Repeat Password', validators=[DataRequired(), EqualTo('password')])
    submit = SubmitField('Request Password Reset')

And here is the corresponding HTML template:

app/templates/reset_password.html: Password reset form template.

{% extends "base.html" %}

{% block content %}
    <h1>Reset Your Password</h1>
    <form action="" method="post">
        {{ form.hidden_tag() }}
            {{ form.password.label }}<br>
            {{ form.password(size=32) }}<br>
            {% for error in form.password.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
            {{ form.password2.label }}<br>
            {{ form.password2(size=32) }}<br>
            {% for error in form.password2.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
        <p>{{ form.submit() }}</p>
{% endblock %}

The password reset feature is now complete, so make sure you try it.

Asynchronous Emails

If you are using the simulated email server that Python provides you may not have noticed this, but sending an email slows the application down considerably. All the interactions that need to happen when sending an email make the task slow, it usually takes a few seconds to get an email out, and maybe more if the email server of the addressee is slow, or if there are multiple addressees.

What I really want is for the send_email() function to be asynchronous. What does that mean? It means that when this function is called, the task of sending the email is scheduled to happen in the background, freeing the send_email() to return immediately so that the application can continue running concurrently with the email being sent.

Python has support for running asynchronous tasks, actually in more than one way. The threading and multiprocessing modules can both do this. Starting a background thread for email being sent is much less resource intensive than starting a brand new process, so I'm going to go with that approach:

app/email.py: Send emails asynchronously.

from threading import Thread
# ...

def send_async_email(app, msg):
    with app.app_context():

def send_email(subject, sender, recipients, text_body, html_body):
    msg = Message(subject, sender=sender, recipients=recipients)
    msg.body = text_body
    msg.html = html_body
    Thread(target=send_async_email, args=(app, msg)).start()

The send_async_email function now runs in a background thread, invoked via the Thread() class in the last line of send_email(). With this change, the sending of the email will run in the thread, and when the process completes the thread will end and clean itself up. If you have configured a real email server, you will definitely notice a speed improvement when you press the submit button on the password reset request form.

You probably expected that only the msg argument would be sent to the thread, but as you can see in the code, I'm also sending the application instance. When working with threads there is an important design aspect of Flask that needs to be kept in mind. Flask uses contexts to avoid having to pass arguments across functions. I'm not going to go into a lot of detail on this, but know that there are two types of contexts, the application context and the request context. In most cases, these contexts are automatically managed by the framework, but when the application starts custom threads, contexts for those threads may need to be manually created.

There are many extensions that require an application context to be in place to work, because that allows them to find the Flask application instance without it being passed as an argument. The reason many extensions need to know the application instance is because they have their configuration stored in the app.config object. This is exactly the situation with Flask-Mail. The mail.send() method needs to access the configuration values for the email server, and that can only be done by knowing what the application is. The application context that is created with the with app.app_context() call makes the application instance accessible via the current_app variable from Flask.


  • #251 Michael Li said 2020-11-22T03:48:20Z

    Hi Miguel,

    Thanks for the great tutorial!

    In app/models.py, for the class "User", why do you define "check_password(self, password)" as instance method while "verify_reset_password_token(token)" as static method?

    class User(UserMixin, db.Model): # ... def check_password(self, password): return check_password_hash(self.password_hash, password)

    # ... @staticmethod def verify_reset_password_token(token): try: # ... # ...
  • #252 Miguel Grinberg said 2020-11-22T10:15:03Z

    @Michael: A token can be checked on its own, without knowing any other information about the user. A password can only be checked if you also know the username. For that reason, when checking passwords you call a method of the User class, and when checking tokens you call it directly on the class.

  • #253 Andrew Wei said 2020-11-29T17:13:58Z

    Hi Miguel,

    I've been following along with your tutorial and it has been a great resource! I'd like to suggest one small change to your instructions to help out others who ran into a similar issue as myself:

    In the send_password_reset_email(user) function in email.py, I would replace the reference to 'ADMINS' with 'MAIL_USERNAME' instead.

    The 'ADMINS' variable was defined in part 7, but this part defines 'MAIL_USERNAME' and 'MAIL_PASSWORD' instead. I used different email address for the two variables, which ended up causing an error. I ended up replacing the line sender=app.config['ADMINS'][0], with sender=app.config['MAIL_USERNAME'], to fix the issue.

    Thanks again for sharing this tutorial! - Andrew

  • #254 Anya Precious said 2020-11-30T01:51:32Z

    Hi Miguel, I'm amazed by this awesome work of yours! On the side note, I would be glad if you'd explain the need of signed signature. I copied the token from my email and pasted it into JWT debugger, the signature showed not signed but still decoded the token. I clicked the link again from my email and it wasn't broken. I'm worried!

  • #255 Miguel Grinberg said 2020-12-01T10:17:23Z

    @Andrew: I'm not sure what was the error that you experienced. All the variables have been defined in Chapter 7, including MAIL_USERNAME. The purpose of this variable is to authenticate to your email server, not to set the sender. In many cases the authenticated user and the sender are the same, but they do not need to be, so it is better to have a separate setting for the sender.

  • #256 Miguel Grinberg said 2020-12-01T10:19:13Z

    @Anya: what are you worried about? The token is not encrypted, the signature just protects against tampering. The idea is that it is not possible to generate valid tokens without knowing the secret signing key, not to keep the contents of the token secret.

  • #257 Andrew Wei said 2020-12-01T23:31:26Z

    @Miguel: Thank you for the response. I noticed that my error was that I kept my ADMIN variable set to [''your-email@example.com''] instead of putting in a real email address, which was what caused the error. It turns out, at least for the email server that I'm using (Zoho), the sender address needs to equal MAIL_USERNAME for it to send the message out.

  • #258 Po Dara said 2020-12-17T09:46:20Z

    Dear Miguel Grinberg I have a problem, when I click on the button "Request Password Reset" after inputting an email in the text field it shows an error as below : TypeError: unsupported operand type(s) for +: 'datetime.time' and 'int'

    Please help me

  • #259 Miguel Grinberg said 2020-12-17T14:21:58Z

    @Po: you are not providing enough information. The error should have included a stack trace, and within it you should have seen the line that caused the error. You need to inspect that line and find what's wrong there.

  • #260 Wanghy said 2020-12-17T14:47:04Z

    Hello Miguel, Thanks for your great tutorials. When I clicked on the submit button "Request Password Reset" to reset the password, nothing happened. And the app logs are as follows, - - [17/Dec/2020 21:59:16] "GET /reset_password/eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJyZXNldF9wYXNzd29yZCI6MSwiZXhw IjoxNjA4MjE0MDgzLjUwOTk2MDJ9.OgbXs_mY1q7DHp6lzJ9WGGeYmXFS16mFgDD3JP8qDJg?csrf_token=IjE4MDljYmQwNGI0ZGU5YTYwNTY2YTNjZGRhYTM2ZWE 3MmJiNGY1MjIi.X9tkLw.ZpjkRvJfdXDYLxRcINxIHgHNJRo&password=ddd&password2=ddd&submit=Request+Password+Reset HTTP/1.1" 200 - - - [17/Dec/2020 21:59:16] "GET /favicon.ico HTTP/1.1" 404 -

    Could you please give me some guidance? What may caused this and how can we debug the application? Thanks in advance.

  • #261 Dara Po said 2020-12-18T10:15:34Z

    Sorry Sir I have a problem, when I click on the button "Request Password Reset" after inputting an email in the text field it shows an error as below : [2020-12-18 17:12:42,804] ERROR in app: Exception on /reset_password_request [POST] Traceback (most recent call last): File "d:\document\my_learning\microblog\venv\lib\site-packages\flask\app.py", line 2447, in wsgi_app response = self.full_dispatch_request() File "d:\document\my_learning\microblog\venv\lib\site-packages\flask\app.py", line 1952, in full_dispatch_request rv = self.handle_user_exception(e) File "d:\document\my_learning\microblog\venv\lib\site-packages\flask\app.py", line 1821, in handle_user_exception reraise(exc_type, exc_value, tb) File "d:\document\my_learning\microblog\venv\lib\site-packages\flask_compat.py", line 39, in reraise raise value File "d:\document\my_learning\microblog\venv\lib\site-packages\flask\app.py", line 1950, in full_dispatch_request rv = self.dispatch_request() File "d:\document\my_learning\microblog\venv\lib\site-packages\flask\app.py", line 1936, in dispatch_request return self.view_functionsrule.endpoint File "D:\Document\My_learning\microblog\app\routes.py", line 202, in reset_password_request send_password_reset_email(user) File "D:\Document\My_learning\microblog\app\email.py", line 15, in send_password_reset_email token = user.get_reset_password_token() File "D:\Document\My_learning\microblog\app\models.py", line 69, in get_reset_password_token {'reset_password': self.id, 'exp': time() + expires_in}, TypeError: unsupported operand type(s) for +: 'datetime.time' and 'int'

  • #262 Miguel Grinberg said 2020-12-18T23:38:52Z

    @Dara: you are importing the wrong time() function, I think. You should use from time import time, not from datetime import time.

    On your second problem, I'm not sure, it seems you are doing some things differently than this tutorial. You are use a GET request for the form submission, which is really not a good idea. Why is that? I recommend that you work with the instructions in this tutorial, and only once you get everything to work you make the changes that you'd like.

  • #263 Darakh said 2020-12-21T10:32:37Z

    Dear sir

    I have a problem when submit reset password request as below : - - [21/Dec/2020 17:30:26] "?[37mGET /login HTTP/1.1?[0m" 200 - - - [21/Dec/2020 17:30:27] "?[37mGET /reset_password_request HTTP/1.1?[0m" 200 - [2020-12-21 17:30:33,856] ERROR in app: Exception on /reset_password_request [POST] Traceback (most recent call last): File "d:\document\my_learning\microblog\venv\lib\site-packages\flask_mail.py", line 492, in send message.send(connection) File "d:\document\my_learning\microblog\venv\lib\site-packages\flask_mail.py", line 427, in send connection.send(self) File "d:\document\my_learning\microblog\venv\lib\site-packages\flask_mail.py", line 188, in send self.host.sendmail(sanitize_address(envelope_from or message.sender), File "C:\Users\User\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 856, in sendmail self.ehlo_or_helo_if_needed() File "C:\Users\User\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 604, in ehlo_or_helo_if_needed if not (200 <= self.ehlo()[0] <= 299): File "C:\Users\User\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 444, in ehlo self.putcmd(self.ehlo_msg, name or self.local_hostname) File "C:\Users\User\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 371, in putcmd self.send(str) File "C:\Users\User\AppData\Local\Programs\Python\Python38-32\lib\smtplib.py", line 363, in send raise SMTPServerDisconnected('please run connect() first') smtplib.SMTPServerDisconnected: please run connect() first

    Please help!!

  • #264 Miguel Grinberg said 2020-12-21T19:09:15Z

    @Darakh: this error occurs when your email server credentials are incorrect or missing.

  • #265 Samyak Jain said 2020-12-23T06:59:16Z

    Hi miguel! Awesome tutorial. But I am getting an error when trying to send the password reset mail. Here is the error:

    Traceback (most recent call last): File "c:\users\dell\desktop\flask\microblog\venv\lib\site-packages\flask_mail.py", line 492, in send message.send(connection) File "c:\users\dell\desktop\flask\microblog\venv\lib\site-packages\flask_mail.py", line 427, in send connection.send(self) File "c:\users\dell\desktop\flask\microblog\venv\lib\site-packages\flask_mail.py", line 192, in send message.rcpt_options) File "C:\Users\Dell\AppData\Local\Programs\Python\Python37\lib\smtplib.py", line 852, in sendmail self.ehlo_or_helo_if_needed() File "C:\Users\Dell\AppData\Local\Programs\Python\Python37\lib\smtplib.py", line 600, in ehlo_or_helo_if_needed if not (200 <= self.ehlo()[0] <= 299): File "C:\Users\Dell\AppData\Local\Programs\Python\Python37\lib\smtplib.py", line 440, in ehlo self.putcmd(self.ehlo_msg, name or self.local_hostname) File "C:\Users\Dell\AppData\Local\Programs\Python\Python37\lib\smtplib.py", line 367, in putcmd self.send(str) File "C:\Users\Dell\AppData\Local\Programs\Python\Python37\lib\smtplib.py", line 359, in send raise SMTPServerDisconnected('please run connect() first') smtplib.SMTPServerDisconnected: please run connect() first

    Why is this happening?

  • #266 Miguel Grinberg said 2020-12-23T11:08:38Z

    @Samyak: This happens because you are not passing your correct email credentials as environment variables. Fix your email credentials and you'll be fine.

  • #267 Anand Jebakumar said 2020-12-27T03:27:27Z

    Hi Miguel! Great series. I noticed that in get_reset_password_token, the decode('utf-8') doesn't work, but removing it work. Just wanted to confirm if this is a recent change. Thanks, Anand!

  • #268 Edward said 2020-12-27T15:46:28Z

    Hello maybe you have an idea why am i getting this error after completing this chapter. As well i tried looking into your code from GitHub and everything looks similar.

    File "/app/routes.py", line 103, in reset_password_request send_password_reset_email(user) File "/app/email.py", line 20, in send_password_reset_email token = user.get_reset_password_token() File "/app/models.py", line 65, in get_reset_password_token return jwt.encode( AttributeError: 'str' object has no attribute 'decode'

    Thank you for creating this awesome tutorial! I'm really interested to start creating real projects with python+flask after this!

    Thank you!

  • #269 Miguel Grinberg said 2020-12-28T00:04:56Z

    @Anand and @Edward: the new release of pyjwt does not require the decode. I'll update the tutorial.

  • #270 Matthew Foulk said 2021-01-01T18:20:48Z

    Hello, I am new to the idea of asynchronous tasks and have a question if you have a chance to answer. Is there a reason why you chose to use multi-threading instead of an async/await coroutine? Is this even possible with coroutines or does that not make sense in this context? Thanks in advance!

  • #271 Miguel Grinberg said 2021-01-01T18:23:47Z

    @Matthew: Flask is not compatible with asyncio and async coroutines, so that is not really an option.

  • #272 Emilio said 2021-01-02T13:51:01Z

    Problem: " raise SMTPServerDisconnected('please run connect() first') smtplib.SMTPServerDisconnected: please run connect() first" .


    1st. Don't replace, in the config.py file, the MAIL_SERVER, MAIL_PORT, MAIL_USE_TLS, MAIL_USERNAME nor the MAIL_PASSWORD with their respective values. Set the environment variables in the terminal but leave the config.py file as the tutorial says for each variable( MAIL_PASSWORD = os.environ.get('MAIL_PASSWORD')). Basically, don't do in your config.py file -> MAIL_SERVER = os.environ.get('smtp.googlemail.com') because you are killing it. :)

    2nd. If you configured App Passwords in gmail, then you should set the 16 character password as the enviroment variable.

    3rd. In the terminal, you can check the value of the environment variables with the printenv command(mac).

    Gracias por el tutorial, Miguel. Muy bien logrado.

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