I have Comcast as an ISP. I'm using NAT and have all the ports necessary forward to my local IP. My domain is pointing to Afraid.org DNS servers and I have MX records for mydomain.com and mail.mydomain.com and an A record for mydomain.com.

When I try to send from me@mydomain.com to my Comcast email address I get this in return:

Code:
This is the Postfix program at host mail.mydomain.com

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 

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

			The Postfix program

: host gateway-a.comcast.net[204.127.225.26] said: 550
    68.52.XX.XX blocked by ldap:ou=rblmx,dc=comcast,dc=net -> Comcast.net
    subscribers are not permitted to directly connect to this mail server. If
    you are a Comcast Commercial Services customer and need support, please
    contact support_biz@cable.comcast.com (in reply to MAIL FROM command)
Reporting-MTA: dns; mail.mydomain.com
X-Postfix-Queue-ID: 9D0BC1A751C
X-Postfix-Sender: rfc822; me@mydomain.com
Arrival-Date: Mon, 12 Mar 2007 14:53:21 -0500 (CDT)

Final-Recipient: rfc822; mycomcastaccountname@comcast.net
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; host gateway-a.comcast.net[204.127.225.26] said:
    550 68.52.XX.XX blocked by ldap:ou=rblmx,dc=comcast,dc=net -> Comcast.net
    subscribers are not permitted to directly connect to this mail server. If
    you are a Comcast Commercial Services customer and need support, please
    contact support_biz@cable.comcast.com (in reply to MAIL FROM command)
Should I change my SMTP port to something other than 25?