内部サーバエラーでメール送信できない

[2023-01-06 19:30:51,183] ERROR in app: Exception on /contact/complete [POST]
Traceback (most recent call last):
  File "C:\Users\tsuch\venv\Lib\site-packages\flask_mail.py", line 492, in send
    message.send(connection)
  File "C:\Users\tsuch\venv\Lib\site-packages\flask_mail.py", line 427, in send
    connection.send(self)
  File "C:\Users\tsuch\venv\Lib\site-packages\flask_mail.py", line 177, in send
    assert message.sender, (
AssertionError: The message does not specify a sender and a default sender has not been configured

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\tsuch\venv\Lib\site-packages\flask\app.py", line 2525, in wsgi_app
    response = self.full_dispatch_request()
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\tsuch\venv\Lib\site-packages\flask\app.py", line 1822, in full_dispatch_request
    rv = self.handle_user_exception(e)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\tsuch\venv\Lib\site-packages\flask\app.py", line 1820, in full_dispatch_request
    rv = self.dispatch_request()
         ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\tsuch\venv\Lib\site-packages\flask\app.py", line 1796, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\tsuch\flaskbook\apps\minimalapp\app.py", line 109, in contact_complete
    send_email(
  File "C:\Users\tsuch\flaskbook\apps\minimalapp\app.py", line 129, in send_email
    mail.send(msg)
  File "C:\Users\tsuch\venv\Lib\site-packages\flask_mail.py", line 491, in send
    with self.connect() as connection:
  File "C:\Users\tsuch\venv\Lib\site-packages\flask_mail.py", line 152, in __exit__
    self.host.quit()
  File "C:\Users\tsuch\AppData\Local\Programs\Python\Python311\Lib\smtplib.py", line 1004, in quit
    res = self.docmd("quit")
          ^^^^^^^^^^^^^^^^^^
  File "C:\Users\tsuch\AppData\Local\Programs\Python\Python311\Lib\smtplib.py", line 431, in docmd
    self.putcmd(cmd, args)
  File "C:\Users\tsuch\AppData\Local\Programs\Python\Python311\Lib\smtplib.py", line 378, in putcmd
    self.send(f'{s}{CRLF}')
  File "C:\Users\tsuch\AppData\Local\Programs\Python\Python311\Lib\smtplib.py", line 365, in send
    raise SMTPServerDisconnected('please run connect() first')
smtplib.SMTPServerDisconnected: please run connect() first
127.0.0.1 - - [06/Jan/2023 19:30:51] "POST /contact/complete HTTP/1.1" 500 -

# loggingをインポート
import logging
import os

from email_validator import EmailNotValidError, validate_email

# Flaskクラスをインポート
from flask import (
    Flask,
    current_app,
    flash,
    g,
    redirect,
    render_template,
    request,
    url_for,
)
from flask_debugtoolbar import DebugToolbarExtension
from flask_mail import Mail, Message

# Flaskクラスをインスタンス化
app = Flask(__name__)
# secret_keyの追加
app.config["SECRET_KEY"] = "2AZSMss3p5QPbcY2hBsJ"
# ログレベルの設定
app.logger.setLevel(logging.DEBUG)

app.logger.debug("DEBUG")
app.logger.info("INFO")
app.logger.warning("WARNING")
app.logger.error("ERROR")
app.logger.critical("CRITICAL")


app.config["DEBUG_TB_INTERCEPT_REDIRECTS"] = False
toolbor = DebugToolbarExtension(app)

# URLと実行する関数をマッピング
@app.route("/")
def index():
    return "Hello,Flaskbook!"


@app.route("/hello/<name>", methods=["GET", "POST"], endpoint="hello-endpoint")
def hello(name):
    return f"Hello, {name}!"


@app.route("/name/<name>")
def show_name(name):
    return render_template("index.html", name=name)


with app.test_request_context():
    # /
    print(url_for("index"))
    # /hello/world
    print(url_for("hello-endpoint", name="world"))
    # /name/Rikuo?page=1
    print(url_for("show_name", name="Rikuo", page="1"))

ctx = app.app_context()
ctx.push()

print(current_app.name)

g.connection = "connection"
print(g.connection)

with app.test_request_context("/users?update=ture"):
    print(request.args.get("updated"))


@app.route("/contact")
def contact():
    return render_template("contact.html")


@app.route("/contact/complete", methods=["GET", "POST"])
def contact_complete():
    if request.method == "POST":
        username = request.form["username"]
        email = request.form["email"]
        description = request.form["description"]
        is_valid = True

        if not username:
            flash("ユーザ名は必須です")
            is_valid = False

        if not email:
            flash("メールアドレスは必須です")
            is_valid = False

        try:
            validate_email(email)
        except EmailNotValidError:
            flash("メールアドレスの形式で入力してください")
            is_valid = False

        if not description:
            flash("問い合わせ内容は必須です")
            is_valid = False

        if not is_valid:
            return redirect(url_for("contact"))

        # メールを送る
        send_email(
            email,
            "お問い合わせありがとうございました。",
            "contact_mail",
            username=username,
            description=description,
        )

        flash("問い合わせ内容はメールにて送信しました。問い合わせありがとうございます。")

        return redirect(url_for("contact_complete"))

    return render_template("contact_complete.html")


def send_email(to, subject, template, **kwargs):
    """メールを送信する関数"""
    msg = Message(subject, recipients=[to])
    msg.body = render_template(template + ".txt", **kwargs)
    msg.html = render_template(template + ".html", **kwargs)
    mail.send(msg)


# Mailクラスのコンフィグを追加
app.config["MAIL_SERVER"] = os.environ.get("MAIL_SERVER")
app.config["MAIL_PORT"] = os.environ.get("MAIL_PORT")
app.config["MAIL_USE_TLS"] = os.environ.get("MAIL_USE_TLS")
app.config["MAIL_USERNAME"] = os.environ.get("MAIL_USERNAME")
app.config["MAIL_PASSWORD"] = os.environ.get("MAIL_PASSWORD")
app.config["MAIL_DEFAULT_SENDER"] = os.environ.get("MAIL_DEFAULT_SENDER")

mail = Mail(app)