Flask Web Development

Chapter 6. Email

Many types of applications need to notify users when certain events occur, and the usual method of communication is email. Although the smtplib package from the Python standard library can be used to send email inside a Flask application, the Flask-Mail extension wraps smtplib and integrates it nicely with Flask.

Email Support with Flask-Mail

Flask-Mail is installed with pip:

(venv) $ pip install flask-mail

The extension connects to a Simple Mail Transfer Protocol (SMTP) server and passes emails to it for delivery. If no configuration is given, Flask-Mail connects to localhost at port 25 and sends email without authentication. Table 6-1 shows the list of configuration keys that can be used to configure the SMTP server.

Table 6-1. Flask-Mail SMTP server configuration keys

Key	Default	Description
MAIL_HOSTNAME	localhost	Hostname or IP address of the email server
MAIL_PORT	25	Port of the email server
MAIL_USE_TLS	False	Enable Transport Layer Security (TLS) security
MAIL_USE_SSL	False	Enable Secure Sockets Layer (SSL) security
MAIL_USERNAME	None	Mail account username
MAIL_PASSWORD	None	Mail account password

During development it may be more convenient to connect to an external SMTP server. As an example, Example 6-1 shows how to configure the application to send email through a Google Gmail account.

Example 6-1. hello.py: Flask-Mail configuration for Gmail

import os
# ...
app.config['MAIL_SERVER'] = 'smtp.googlemail.com'
app.config['MAIL_PORT'] = 587
app.config['MAIL_USE_TLS'] = True
app.config ...