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
KeyDefaultDescription

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 ...

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