Using authentication to send emails

[loeffelpan]

I trying to integrate simplelogin into another mailserver I have already running.
I'm able to receive mails for my simplelogin domain and they are forwarded to sl-email-container. And I can see that simplelogin is trying to forward that email correctly to my real mailbox, but cannot send it through port 25 to mailserver.

sl-email  | 2024-06-08 09:10:10,965 - SL - DEBUG - 1 - "/code/email_handler.py:967" - forward_email_to_mailbox() - 886C8880B342 - Forward mail from [email protected] to [email protected], mail_options:['SIZE=36082', 'BODY=7BIT'], rcpt_options:[]
sl-email  | 2024-06-08 09:10:20,884 - SL - ERROR - 1 - "/code/app/mail_sender.py:196" - _send_to_smtp() - 886C8880B342 - Could not send message to smtp server mailserver:25
sl-email  | Traceback (most recent call last):
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 398, in getreply
sl-email  |     line = self.file.readline(_MAXLINE + 1)
sl-email  |   File "/usr/local/lib/python3.10/socket.py", line 705, in readinto
sl-email  |     return self._sock.recv_into(b)
sl-email  | TimeoutError: timed out
sl-email  |
sl-email  | During handling of the above exception, another exception occurred:
sl-email  |
sl-email  | Traceback (most recent call last):
sl-email  |   File "/code/app/mail_sender.py", line 148, in _send_to_smtp
sl-email  |     with SMTP(
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 255, in __init__
sl-email  |     (code, msg) = self.connect(host, port)
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 343, in connect
sl-email  |     (code, msg) = self.getreply()
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 401, in getreply
sl-email  |     raise SMTPServerDisconnected("Connection unexpectedly closed: "
sl-email  | smtplib.SMTPServerDisconnected: Connection unexpectedly closed: timed out
sl-email  |
sl-email  | During handling of the above exception, another exception occurred:
sl-email  |
sl-email  | Traceback (most recent call last):
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 398, in getreply
sl-email  |     line = self.file.readline(_MAXLINE + 1)
sl-email  |   File "/usr/local/lib/python3.10/socket.py", line 705, in readinto
sl-email  |     return self._sock.recv_into(b)
sl-email  | TimeoutError: timed out
sl-email  |
sl-email  | During handling of the above exception, another exception occurred:
sl-email  |
sl-email  | Traceback (most recent call last):
sl-email  |   File "/code/app/mail_sender.py", line 148, in _send_to_smtp
sl-email  |     with SMTP(
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 255, in __init__
sl-email  |     (code, msg) = self.connect(host, port)
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 343, in connect
sl-email  |     (code, msg) = self.getreply()
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 401, in getreply
sl-email  |     raise SMTPServerDisconnected("Connection unexpectedly closed: "
sl-email  | smtplib.SMTPServerDisconnected: Connection unexpectedly closed: timed out
sl-email  |
sl-email  | During handling of the above exception, another exception occurred:
sl-email  |
sl-email  | Traceback (most recent call last):
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 398, in getreply
sl-email  |     line = self.file.readline(_MAXLINE + 1)
sl-email  |   File "/usr/local/lib/python3.10/socket.py", line 705, in readinto
sl-email  |     return self._sock.recv_into(b)
sl-email  | TimeoutError: timed out
sl-email  |
sl-email  | During handling of the above exception, another exception occurred:
sl-email  |
sl-email  | Traceback (most recent call last):
sl-email  |   File "/code/app/mail_sender.py", line 148, in _send_to_smtp
sl-email  |     with SMTP(
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 255, in __init__
sl-email  |     (code, msg) = self.connect(host, port)
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 343, in connect
sl-email  |     (code, msg) = self.getreply()
sl-email  |   File "/usr/local/lib/python3.10/smtplib.py", line 401, in getreply
sl-email  |     raise SMTPServerDisconnected("Connection unexpectedly closed: "
sl-email  | smtplib.SMTPServerDisconnected: Connection unexpectedly closed: timed out
sl-email  | 2024-06-08 09:10:20,892 - SL - INFO - 1 - "/code/email_handler.py:2437" - _handle() - 886C8880B342 - Finish mail_from [email protected], rcpt_tos ['[email protected]'], takes 10.103663682937622 seconds with return code '250 Message accepted for delivery'<<===

I'm pretty sure, that this is due to my mailserver is not enabled to send mails unauthenticated through port 25.
Is it possible to send mails from simplelogin using submission (including authentication)?