I'm trying to use the Email marketing module in Odoo 16 Community on a VPS, with a custom mail server. When I go to Incoming and Outgoing Mail and test the connection it tells me that a connection has been established.

But when I go to send an email from the module it won't let me. And when I try to send it from Settings/Technical/Emails it gives me this error:

RPC_ERROR

Odoo Server Error

Traceback (most recent call last):

  File "/opt/odoo/odoo-server/odoo/http.py", line 1632, in _serve_db

    return service_model.retrying(self._serve_ir_http, self.env)

  File "/opt/odoo/odoo-server/odoo/service/model.py", line 133, in retrying

    result = func()

  File "/opt/odoo/odoo-server/odoo/http.py", line 1659, in _serve_ir_http

    response = self.dispatcher.dispatch(rule.endpoint, args)

  File "/opt/odoo/odoo-server/odoo/http.py", line 1863, in dispatch

    result = self.request.registry['ir.http']._dispatch(endpoint)

  File "/opt/odoo/odoo-server/addons/website/models/ir_http.py", line 237, in _dispatch

    response = super()._dispatch(endpoint)

  File "/opt/odoo/odoo-server/odoo/addons/base/models/ir_http.py", line 154, in _dispatch

    result = endpoint(**request.params)

  File "/opt/odoo/odoo-server/odoo/http.py", line 716, in route_wrapper

    result = endpoint(self, *args, **params_ok)

  File "/opt/odoo/odoo-server/addons/web/controllers/dataset.py", line 46, in call_button

    action = self._call_kw(model, method, args, kwargs)

  File "/opt/odoo/odoo-server/addons/web/controllers/dataset.py", line 33, in _call_kw

    return call_kw(request.env[model], method, args, kwargs)

  File "/opt/odoo/odoo-server/odoo/api.py", line 468, in call_kw

    result = _call_kw_multi(method, model, args, kwargs)

  File "/opt/odoo/odoo-server/odoo/api.py", line 453, in _call_kw_multi

    result = method(recs, *args, **kwargs)

  File "/opt/odoo/odoo-server/addons/mail/models/mail_mail.py", line 449, in send

    smtp_session.quit()

  File "/usr/lib/python3.10/smtplib.py", line 1004, in quit

    res = self.docmd("quit")

  File "/usr/lib/python3.10/smtplib.py", line 431, in docmd

    self.putcmd(cmd, args)

  File "/usr/lib/python3.10/smtplib.py", line 378, in putcmd

    self.send(f'{s}{CRLF}')

  File "/usr/lib/python3.10/smtplib.py", line 365, in send

    raise SMTPServerDisconnected('please run connect() first')

smtplib.SMTPServerDisconnected: please run connect() first

The above server error caused the following client error:

RPC_ERROR://dominio.com/web/assets/1939-d73ea71/web.assets_backend.min.js:995:163)

    at XMLHttpRequest.<anonymous> (https://dominio.com/web/assets/1939-d73ea71/web.assets_backend.min.js:1003:13)

What could it be?