unable to send emails using global smtp settings

I am trying to establish a global smtp setting for email notification. If I edit traccar.xml file as suggested in multiple threads it will neither send the mail nor throw an error. However if I edit specific user settings in traccar UI the mails will be sent. Without an error it is very hard to find my mistake. Any help will be greatly appreciated.

Here is traccar.xml file content:

<entry key='mail.smtp.host'>mail.stamm-networks.de</entry>
<entry key='mail.smtp.port'>587</entry>
<entry key='mail.smtp.starttls.enable'>true</entry>
<entry key='mail.smtp.from'>service@gpsys.de</entry>
<entry key='mail.smtp.auth'>true</entry>
<entry key='mail.smtp.username'>service@gpsys.de</entry>
<entry key='mail.smtp.password'>****</entry>

Thanks in advance

If it doesn't give as error and you are sure you configured email notifications correctly, it probably means that your provider successfully accepts the messages.

what does that mean and what do I need to do to receive the mails as expected in mail inbox of users?

I'm also confused. What is not working? What email are you expecting to see?

What I am trying is sending a test mail with notification message from traccars ui and receive this mail with any users email account.
If I type the above credentials manually via traccar ui into any user account, sending and receiving notifications via mail works well, but if I store the same credentials globally in config/traccar.xml it is not working.
I want them to be stored and used in the xml file, not individually in the users settings.
Hope this explains the point a bit better.

There should be no difference. If it doesn't work, you are missing something and you need to carefully review your settings and config.