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How to Send and Receive Emails from Your Flask App using Twilio SendGrid

SendGrid is a communication platform for transactional and marketing email. The goal of using SendGrid is technically delivering an exceptional email experience since email is the backbone of a business' customer engagement. In this tutorial, I will show you how you can build a Flask application and integrate Twilio SendGrid APIs.

What we will do:

  1. Create a SendGrid account
  2. Build a Flask application
  3. Integrate Flask mail
  4. Integrate Twilio SendGrid

Create a SendGrid account

  • Create a free account now
  • Log into your account
  • Select Settings then click on API Keys
  • Create a new API Key by clicking on the blue button

Create SendGrid API Key

  • Give the API Key a name
  • Ensure you select Full Access
  • Click Create and View button

Copy the API Key and save it somewhere safe. You will need it later.

Build a Flask Application

Login Demo

Build this application in Flask. The mandatory user authentication process can be optional for now. To get you started, consider to use this structure:

sendgrid_project
    | ----------- sendgrid.py
    | ----------- config.py
    | ----------- .env
    | ----------- .env-template
    | ----------- .gitignore
    | ----------- .flaskenv
    | ----------- requirements.txt
    | ----------- app/
                   | ----------- routes.py
                   | ----------- forms.py
                   | ----------- __init__.py
                   | ----------- models.py
                   | ----------- emails.py.py
                   | ----------- errors.py
                   | ----------- templates/
                                    | ----------- home.html
                                    | ----------- base.html
                                    | ----------- register.html
                                    | ----------- login.html
                                    | ----------- password_reset_request.html
                                    | ----------- password_reset.html
                                    | ----------- emails/
                                                    | ----------- password_reset.html
                                                    | ----------- password_reset.txt
                    | ----------- static/
                                    | ----------- styles.css

Use the commands mkdir and touch in your terminal to quickly create this structure

# Create an empty directory
$ mkdir sendgrid_project

# Create an empty file inside an existing directory
$ touch sendgrid_projcet/config.py

Activate your virtual environment:

$ mkvirtualenv # I am using a virtualenvwrapper

Next, install packages that will be used in the project:

  • flask
  • flask-sqlalchemy
  • flask-migrate
  • flask-mail
  • flask_bootstrap
  • flask-wtf
  • flask-login
  • email-valiator
  • pyjwt
  • pyngrok
(venv)$ pip3 install flask flask-migrate # add the rest here

Add the installed packages in requirements.txt file:

(venv)$ pip3 freeze > requirements.txt

Complete the application as seen in this GitHub repository.

Noteworthy, the files in app/templates/email carry the message that will be sent to a user's email. This email message has a password reset link which will redirect a user to another page of the application where they can reset their password. This link has an expiration period after which it will become invalid.

Also, it should be noted the application does send errors to the admin of the application whenever there is an internal server error. This email bears the message of the error so the admin can see the actual cause problem.

Testing How to Send Password Reset Email Locally

Password Reset

  • Register a user using a valid and working email, for example johndoe@gmail.com. You should be able to access this email.
  • Log in to your app to make sure your credentials actually work.
  • Log out of the app by clickig Logout link at the top-right of the navbar
  • Click on Reset Password link
  • Add the registered user's email
  • Open the user's email to find the password reset request email
  • Click on the expirable link in the email
  • Type in your new password and confirm it
  • Click Reset Password button
  • Click on the Login link
  • Enter your new password

You should be able to log in. From your terminal, you should have seen how the email authentication works.

Sending Emails Using Twilio SendGrid

Now that you know how to send emails using Flask Mail, you can do the same for applications that are on production. If you host this application, say in Heroku, you will note that the password reset feature does not work. You have no errors, but still it does not work. This is because the email service we are using does not work on production. And that is where Twilio SendGrid comes it.

In this section, I am going to show you how to send emails using Twilio SendGrid. The method I will use below will not work on a production software.

You have already signed up for Twilio SendGrid and you have your API Key with you. We will make use of this email module we have set up to work with Twilio SendGrid.

First, let us update the config.py file to use SendGrid configurations:

config.py: Set SendGrid environment variables

# Current Email configurations
MAIL_SERVER = os.environ.get('MAIL_SERVER')
MAIL_PORT = int(os.environ.get('MAIL_PORT') or 25)
MAIL_USE_TLS = os.environ.get('MAIL_USE_TLS') is not None
MAIL_USERNAME = os.environ.get('MAIL_USERNAME')
MAIL_PASSWORD = os.environ.get('MAIL_PASSWORD')
ADMINS = ['your-email@example.com']

# SendGrid's email configurations
MAIL_SERVER = os.environ.get('MAIL_SERVER')
MAIL_PORT = int(os.environ.get('MAIL_PORT') or 25)
MAIL_USE_TLS = os.environ.get('MAIL_USE_TLS') is not None
MAIL_USERNAME = os.environ.get('MAIL_USERNAME')
MAIL_PASSWORD = os.environ.get('SENDGRID_API_KEY')
MAIL_DEFAULT_SENDER = os.environ.get('MAIL_DEFAULT_SENDER')

To use SendGrid's SMTP Service, you have to properly update your configurations.

  • The mail server will be smpt.sendgrid.net
  • The mail port should be 587 (or 25)
  • TLS must be enabled
  • For your username, do not use your email address, rather you must use the word "apikey"

This is how your .env file will look like:

MAIL_SERVER='smtp.sendgrid.net'
MAIL_PORT='587'
MAIL_USE_TLS='True'
MAIL_USERNAME='apikey'
SENDGRID_API_KEY='add-your-api-key-here'
MAIL_DEFAULT_SENDER='a-valid-and-working-email-address'

In the current application, you will need to update all instances of the variable ADMINS to MAIL_DEFAULT_SENDER.

Then run your flask shell:

(venv) flask shell

# Output
Python-dotenv could not parse statement starting at line 1
Python 3.8.5 (default, Jan 27 2021, 15:41:15) 
[GCC 9.3.0] on linux
App: app [development]
Instance: /home/harry/email_support_in_flask/instance
>>> app

# Output
<Flask 'app'>

What does the flask shell command do? The purpose of the flask shell command is to start the Python interpreter in the context of the application. Take this example:

(venv)$ python # this starts the python intepreter

# Output
Python 3.8.5 (default, Jan 27 2021, 15:41:15) 
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> app
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'app' is not defined
>>>

Python does not recognize the app instance unless it is explicitly imported. From the flask shellexample above, you will notice that the Python interpreter recongized the app instance. This is all defined in the application entry file sendgrid.py at the project's top-level directory.

With your Python interpreter open using the flask shell command, we will import flask_mail to send out an example email.

>>> from app import mail
>>> from flask_mail import Message

>>> msg = Message('Sending Email Using Twilio SendGrid', recipients=['a-working-recipient-email-address'])
>>> msg.body = 'Hi, \n\n This is a test email that I have sent you. It has no significance to you whatsoever, but to me it means a lot. You can ignore this message. \n\nFlask Email Support Team'
>>>msg.html = '<p>Hi, <br><br> This is a test email that I have sent you. It has no significance to you whatsoever, but to me it means a lot. You can ignore this message. <br><br>Flask Email Support Team</p>'

>>>mail.send(msg)

You will get the error:

# ...
AssertionError: The message does not specify a sender and a default sender has not been configured

To fix this error, you need to configure your account to specify a Sender Identity. We will use the Single Sender Verification which is a fast way to verify your Sender Identity when you don’t have access to the DNS settings for your domain.

Create Sender

  • Provide valid and working email addresses for From Email Address and Reply To form fields. You can fill in placeholder data in the other fields.

That's how you specify a sender identity. Note that this is used for test purposes only. With a trial account you can send 100 emails per day forever.

In your .env file, update the MAIL_DEFAULT_SENDER variable to be the same as the one you have set up just now in your Sender Identity.

Exit the Python interpreter above by pressing Ctrl + Z. Run flask shell to start all over again.

>>> from app import mail
>>> from flask_mail import Message

>>> msg = Message('Sending Email Using Twilio SendGrid', recipients=['any-working-recipient-email-address'])
>>> msg.body = 'Hi, \n\n This is a test email that I have sent you. It has no significance to you whatsoever, but to me it means a lot. You can ignore this message. \n\nFlask Email Support Team'
>>>msg.html = '<p>Hi, <br><br> This is a test email that I have sent you. It has no significance to you whatsoever, but to me it means a lot. You can ignore this message. <br><br>Flask Email Support Team</p>'

>>>mail.send(msg)

Hopefully everything goes well and you have received the test email in your inbox.

Test Email from SendGrid