im not too familiar with postfix. You may have to goolge for this - Postfix -- the Sendmail Replacement
What we do know so far is that your moodle can submit emails to your smtp host, so there's no issues there, but there may be an issue with the config.
We also know there's no connectivity issue so we can focus on the config.
What we need to know is where those messages are sitting and why they are not beong delivered, we have to check the logs, queues, directories....
When I download Postfix at ftp://ftp.is.co.za/networking/mail/m...fix/index.html the extension is tar.gz which is normally for linux is there not a windows one that you know of....