Blocked by blacklist help

Ok, I have gotten my DNS server to work properly. I am able to send and receive email. I am just have trouble sending to an @comcast.net address. I got the following error:

There was a SMTP communication problem with the recipents email server......<mail.xalotech.com #5.5.0 smtp;550-68.80.83.205 blocked by blacklist.mail.ops.asp.att.net.>

I really think it is a reverse look up issue. Am I right?

Cheers!

Yes, because comcast.net has been blacklisted all over the net, on 5 RBL blacklists and 1 more here. Running mail server on comcast account is just asking for troubles.
That's why I previously said if you want to play this toy, you need to invest more money, read here to find out more.