I am on Ubuntu 10.04 and had postfix installed, I can send mail with sendmail but when I send mail to my server through hotmail or alike it just never appears.
I installed mailutils and ran mail while in root (which is who is configured to receive everything) and it said no mail. There was also no mail in /var/mail/root
What steps would I need to do for postfix to start accepting e-mail externally, any specific guides (I prefer not to do virtual users if that is too complex..)
To be able to receive emails from external servers, you need to have a working postfix. From your explanation, it seems that you can send emails locally.
The other important part that you did not talk about is configuring your DNS records and allowing the external servers to send you the emails. You need to define at least one MX record for your domain and point it to your email server. Also, the SMTP port 25 should be opened to your email server.