Send email from Flask with Flask-Mail over SMTP

pip install Flask-Mail

import os
from flask import Flask
from flask_mail import Mail, Message

app = Flask(__name__)
app.config.update(
    MAIL_SERVER=os.environ.get("SMTP_HOST", "smtp.queensmtp.com"),
    MAIL_PORT=int(os.environ.get("SMTP_PORT", "587")),
    MAIL_USE_TLS=True,            # STARTTLS on 587; set MAIL_USE_SSL=True + port 465 instead for implicit TLS
    MAIL_USERNAME=os.environ["SMTP_USER"],
    MAIL_PASSWORD=os.environ["SMTP_PASS"],
    MAIL_DEFAULT_SENDER=("Your App", "hello@yourdomain.com"),
)
mail = Mail(app)

@app.route("/signup", methods=["POST"])
def signup():
    msg = Message("Welcome", recipients=["customer@example.com"])
    msg.body = "Thanks for signing up."
    msg.html = "<p>Thanks for <b>signing up</b>.</p>"
    # with app.open_resource("terms.pdf") as f: msg.attach("terms.pdf", "application/pdf", f.read())
    mail.send(msg)
    return "ok"