SMTP Authentication error on production server

[XanderVertegaal]

This error prevents registration confirmation emails from being sent.

Internal Server Error: /users/registration/
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
               ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/core/handlers/base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/views/decorators/csrf.py", line 56, in wrapper_view
    return view_func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/views/generic/base.py", line 104, in view
    return self.dispatch(request, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/utils/decorators.py", line 46, in _wrapper
    return bound_method(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/views/decorators/debug.py", line 92, in sensitive_post_parameters_wrapper
    return view(request, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/dj_rest_auth/registration/views.py", line 47, in dispatch
    return super().dispatch(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/rest_framework/views.py", line 509, in dispatch
    response = self.handle_exception(exc)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/rest_framework/views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/usr/local/lib/python3.11/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
    raise exc
  File "/usr/local/lib/python3.11/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/rest_framework/generics.py", line 194, in post
    return self.create(request, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/dj_rest_auth/registration/views.py", line 68, in create
    user = self.perform_create(serializer)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/dj_rest_auth/registration/views.py", line 92, in perform_create
    complete_signup(
  File "/usr/local/lib/python3.11/site-packages/allauth/account/utils.py", line 102, in complete_signup
    return flows.signup.complete_signup(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/allauth/account/internal/flows/signup.py", line 114, in complete_signup
    return perform_login(request, login)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/allauth/account/internal/flows/login.py", line 89, in perform_login
    return resume_login(request, login)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/allauth/account/internal/flows/login.py", line 98, in resume_login
    response = ctrl.handle()
               ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/allauth/account/stages.py", line 112, in handle
    response, cont = stage.handle()
                     ^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/allauth/account/stages.py", line 151, in handle
    send_email_confirmation(
  File "/usr/local/lib/python3.11/site-packages/allauth/account/utils.py", line 222, in send_email_confirmation
    return flows.email_verification.send_verification_email(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/allauth/account/internal/flows/email_verification.py", line 263, in send_verification_email
    email_address.send_confirmation(request, signup=signup)
  File "/usr/local/lib/python3.11/site-packages/allauth/account/models.py", line 107, in send_confirmation
    confirmation.send(request, signup=signup)
  File "/usr/local/lib/python3.11/site-packages/allauth/account/models.py", line 136, in send
    get_adapter().send_confirmation_mail(request, self, signup)
  File "/usr/local/lib/python3.11/site-packages/allauth/account/adapter.py", line 671, in send_confirmation_mail
    self.send_mail(email_template, emailconfirmation.email_address.email, ctx)
  File "/usr/local/lib/python3.11/site-packages/allauth/account/adapter.py", line 214, in send_mail
    msg.send()
  File "/usr/local/lib/python3.11/site-packages/django/core/mail/message.py", line 299, in send
    return self.get_connection(fail_silently).send_messages([self])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/core/mail/backends/smtp.py", line 127, in send_messages
    new_conn_created = self.open()
                       ^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/core/mail/backends/smtp.py", line 94, in open
    self.connection.login(self.username, self.password)
  File "/usr/local/lib/python3.11/smtplib.py", line 750, in login
    raise last_exception
  File "/usr/local/lib/python3.11/smtplib.py", line 739, in login
    (code, resp) = self.auth(
                   ^^^^^^^^^^
  File "/usr/local/lib/python3.11/smtplib.py", line 662, in auth
    raise SMTPAuthenticationError(code, resp)
smtplib.SMTPAuthenticationError: (535, b'5.7.3 Authentication unsuccessful')