I have tested and it seems I do have an SMTP server running locally. What I don't know is how to get its url and login credentials. Any idea how to find those?
If it is a standard Ubuntu then you have a Postfix running on it. And there is no user authentication for it. In the default configuration it is only allowed to send mail to local users (not to users elsewhere on the Internet).
You can send mails to any user on your box by just using