What settings should the email server be mindful of to avoid bounce back from major email providers

So I think my postfix+dovecot+roundcube+postfixadmin+sasl+spamassassin+amavisd-new+postgrey setup is working correctly. I can send out emails to certain domain names. Receiving definitely works; however, when i send out emails to hotmail for instance I get a bounce back. Even worse yahoo doesn't even bounce it just kills the email all together.

I don't think I have been blacklisted or anything (maybe I have been? I don't even know.) so I am assuming that these companies don't like that some of my settings don't match up in my headers or something. Perhaps I have an IP or Server name instead of domain name somewhere or something. I am not sure.

Also is there a way to confirm that I have password protected SMTP? I am pretty sure it is; however, How can I be sure?

Here is the bounce back email:

This is the mail system at host XXXXXXX.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

               The mail system  

:
said: 550 OU-001 Mail rejected by Windows Live Hotmail for policy reasons.
Reasons for rejection may be related to content with spam-like
characteristics or IP/domain reputation problems. If you are not an
email/network admin please contact your E-mail/Internet Service Provider
for help. Email/network admins, please visit x for
email delivery information and support (in reply to MAIL FROM command)

Reporting-MTA: dns; XXXXXXXXXXXXXXX
X-Postfix-Queue-ID: C9CD66C0F4
X-Postfix-Sender: rfc822; XXXXXXXX
Arrival-Date: Sun, 4 Oct 2009 23:30:50 +0000 (UTC)

Final-Recipient: rfc822; XXXXX
Original-Recipient: rfc822;XXXXXX
Action: failed
Status: 5.0.0
Remote-MTA: dns; hotmailserver
Diagnostic-Code: smtp; 550 OU-001 Mail rejected by Windows Live Hotmail for
policy reasons. Reasons for rejection may be related to content with
spam-like characteristics or IP/domain reputation problems. If you are not
an email/network admin please contact your E-mail/Internet Service Provider
for help. Email/network admins, please visit x for
email delivery information and support