postfix / windows live mail problems (possibly OT)

[Mark Moellering]

I recently set up a postfix mail server on freebsd 8.1 with dovecot.  I 
am having trouble sending mail using Windows Live Mail.
The error I see in the logfiles is:
Mar 16 13:13:57 mail postfix/smtpd[5159]: connect from 
c-68-40-255-141.hsd1.mi.comcast.net[68.40.255.141]
Mar 16 13:13:57 mail postfix/smtpd[5159]: NOQUEUE: reject: RCPT from 
c-68-40-255-141.hsd1.mi.comcast.net[68.40.255.141]: 554 5.7.1 
<mark at xxxx.com>: Relay access denied; from=<brad at yyyy.com> 
to=<mark at xxxx.com> proto=ESMTP helo=<HPPC>
Mar 16 13:13:57 mail postfix/smtpd[5159]: disconnect from 
c-68-40-255-141.hsd1.mi.comcast.net[68.40.255.141]

The error Windows Live displays is:

Server Error: 554
Server Response: 554 5.7.1 <mark at xxxx.com>: Relay access denied
Server: 'mail.yyyy.com'
Windows Live Mail Error ID: 0x800CCC79
Protocol: SMTP
Port: 587
Secure(SSL): No

If anyone can point me to a better list or otherwise help out, it would 
be greatly appreciated.  Naturally, Thunderbird and KDE-Mail work fine...

Mark Moellering
Class-Creator . com