Flask uses the MVC (Model View Controller) Framework. Just to make this as obvious as possible, I like my Flask apps to have the following.

• Model -> models.py
• View -> views.py
• Controller -> __init__.py

Let's say your Flask app has the following structure.

├── main.py
├── database (directory)
│   ├── example.db
├── my-project (directory)
│   ├── __init__.py
│   ├── views.py
│   ├── models.py
│   ├── templates (directory)
│   │   ├── base.html
│   │   ├── home.html
│   │   ├── results.html
│   └── static (directory)
│       └── custom.css

First, use the pip install command to install the Flask-Mail package.

pip install aws-secretsmanager-caching

Or, you can specify the version to install

pip install Flask-Mail==0.9.1

Or, better yet, use a requirements.txt file.

Flask-Mail==0.9.1

And then install the packages using the requirements.txt file.

pip install --requirement requirements.txt

Your controller (__init__.py) could have something like this.

from flask import Flask
from flask_mail import Mail

mail = Mail()

def app():
    app = Flask(__name__)
    app.config['MAIL_SERVER']   = 'mail.example.com'
    app.config['MAIL_PORT']     = 25
    app.config['MAIL_USERNAME'] = 'john.doe'
    app.config['MAIL_PASSWORD'] = 'itsasecret'
    app.config['MAIL_USE_TLS']  = False
    mail = Mail(app)

    return app

Your view (views.py in this example) could have something like this.

from . import mail
from flask_mail import Message, Mail

@views.route('/sendEmail')
def email():
    msg = Message('Subject Line', sender = 'no-reply@example.com', reply_to = 'john.doe@example.com', recipients = ['jane.doe@example.com'])
    msg.body = "Hello World"
    mail.send(msg)

    try:
        mail.send(msg)
    except Exception as exception:
        return exception
    else:
        return "successfully sent email"

Here is how you could attach a file to the email.

IMPORTANT

The magic module is used to determine the MIME type (e.g. text/plain or application/pdf) and encoding (e.g. us-assii or utf-8) and then uses a try except block to NOT attach the file if doing so would raise an exception. The magic module can be installed using "pip install python-magic"

from . import mail, magic
from flask_mail import Message, Mail

@views.route('/sendEmail')
def email():
    msg = Message('Subject Line', sender = 'no-reply@example.com', reply_to = 'john.doe@example.com', recipients = ['jane.doe@example.com'])
    msg.body = "Hello World"


    mimetype = mime.from_file("C:\\Users\\john.doe\\helloworld.txt")
                
    blob = open("C:\\Users\\john.doe\\helloworld.txt", 'rb').read()
    m = magic.open(magic.MAGIC_MIME_ENCODING)
    m.load()
    encoding = m.buffer(blob)

    file = open("C:\\Users\\john.doe\\helloworld.txt")

    try:
        msg.attach("helloworld.txt", "application/txt", file.read())
    except Exception as exception:
        print(exception)

    file.close()

    try:
        mail.send(msg)
    except Exception as exception:
        return exception
    else:
        return "successfully sent email"