from flask import Flask, render_template, request, jsonify
from flask_mail import Mail, Message

app = Flask(__name__, template_folder='template')

app.config['MAIL_SERVER'] = 'smtp.gmail.com'
app.config['MAIL_PORT'] = 465  # For SSL
app.config['MAIL_USE_TLS'] = False
app.config['MAIL_USE_SSL'] = True
app.config['MAIL_USERNAME'] = 'asker244897@gmail.com'  # your Gmail address
app.config['MAIL_PASSWORD'] = 'your-app-password'  # your Gmail App Password

mail = Mail(app)

@app.route("/")
def home():
    return render_template("index.html", hata="")

@app.route("/users", methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        name = request.form.get('name')
        phone = request.form.get('phone')
        email = request.form.get('email')
        message = request.form.get('message')

        if not name or not phone or not email or not message:
            return render_template("index.html")
        else:
            msg = Message('Subject of the Email', sender=email, recipients=['asker244897@gmail.com'])
            msg.body = f"Name: {name}\nPhone: {phone}\nEmail: {email}\nMessage: {message}"

            mail.send(msg)

            return render_template("index.html", name=name, phone=phone, email=email, message=message, success_message="Your message has been sent!")

    return render_template("index.html", hata="")

if __name__ == "__main__":
    app.run(debug=True)

<section class="contact" id="contact">
    <h2 class="heading">Contact <span>Me!</span></h2>
    <form id="myForm" action="/users" method="post">
        <div class="input-box">
            <input type="text" name="name" placeholder="Name & Surname" required>
            <input type="email" name="email" placeholder="Email Address" required>
            <input type="tel" name="phone" placeholder="Phone Number" required>
        </div>
        <textarea name="message" id="message" cols="30" rows="10" placeholder="Your Message" required></textarea>
        <input type="submit" name="send" value="Send Message" class="btn">
        <div id="notification" style="color: limegreen; font-size: 18px; margin-top: 5px;"></div>
    </form>
</section>