Web-based applications typically require the ability to send mail to the user/client. Flask doesn’t have an out of the box solution to send mail.

Instead, the Flask-Mail extension makes it easy to establish a simple interface with any email server.

Email generally uses two protocols, one for sending mails (smtp) and one for receiving mail (pop3). This article is about sending mails.

Related course: Python Flask: Create Web Apps with Flask

Introduction

First, the Flask-Mail extension should be installed with the help of the pip utility.

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pip install Flask-Mail

You then need to configure the Flask-Mail by setting the values for the following application parameters.

  • MAIL_SERVER
  • MAIL_USE_TLS
  • MAIL_USE_SSL
  • MAIL_DEBUG
  • MAIL_USERNAME
  • MAIL_PASSWORD
  • MAIL_DEFAULT_SENDER
  • MAIL_MAX_EMAILS
  • MAIL_SUPPRESS_SEND
  • MAIL_ASCII_ATTACHMENTS

The flask-mail module contains definitions of the following important classes.

The Mail class manages email messaging requirements.The class constructor takes the form of:

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flask-mail.Mail(app = None)

Mail class methods include: send(), connect() and send_message().

The Message class encapsulated an email.The Message class constructor has several parameters:

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flask-mail.Message(subject, recipients, body, html, sender, cc, bcc, 
   reply-to, date, charset, extra_headers, mail_options, rcpt_options)

Message class method attach () - Add attachment for mail.This method takes the following parameters:

  • filename : The name of the file
  • content_type : MIME type
  • data - file data

You can use add_recipient() to add another recipient to the message.

Mail config and functions

In the example below, the SMTP server for the Google gmail service is used as the MAIL_SERVER for the Flask-Mail configuration.

Step 1: Import the Mail and Message classes from the flask-mail module in the code.

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from flask_mail import Mail, Message

Step 2: Configure server parameters

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app.config['MAIL_SERVER']='smtp.gmail.com'
app.config['MAIL_PORT'] = 465
app.config['MAIL_USERNAME'] = '[email protected]'
app.config['MAIL_PASSWORD'] = '*****'
app.config['MAIL_USE_TLS'] = False
app.config['MAIL_USE_SSL'] = True

Step 3: Create an instance of the Mail class.

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mail = Mail(app)

Step 4: The Message object is set in a Python function that is mapped by the URL rule (‘/‘).

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@app.route("/")
def index():
   msg = Message('Hello', sender = '[email protected]', recipients = ['[email protected]'])
   msg.body = "This is the email body"
   mail.send(msg)
   return "Sent"

Flask mail example

The entire code is as follows.Run the following script in the Python shell and access localhost:5000/.

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from flask import Flask
from flask_mail import Mail, Message

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

app.config['MAIL_SERVER']='smtp.gmail.com'
app.config['MAIL_PORT'] = 465
app.config['MAIL_USERNAME'] = '[email protected]'
app.config['MAIL_PASSWORD'] = '*****'
app.config['MAIL_USE_TLS'] = False
app.config['MAIL_USE_SSL'] = True
mail = Mail(app)

@app.route("/")
def index():
   msg = Message('Hello', sender = '[email protected]', recipients = ['[email protected]'])
   msg.body = "Hello Flask message sent from Flask-Mail"
   mail.send(msg)
   return "Sent"

if __name__ == '__main__':
   app.run(debug = True)

Note that security in the Gmail service can prevent this login attempt. If you use gmail smtp server, you might have to reduce the security level.

Related course: Python Flask: Create Web Apps with Flask