You have been blocked from emailing the Comcast network because we have determined that you are sending email from a dynamic/residential IP address within the Comcast domain. Comcast does not allow subscribers to send email from a mail server other than smtp.comcast.net.
I don't believe my email is originating from a dynamic/residential source.
Your IP space is designated for residential Comcast service. You can send or receive email through the Comcast mail servers by using our webmail application or by configuring your mail client to connect properly. If you need to run your own mail server, please contact our Commercial Services organization at support_biz@cable.comcast.com.
How do I get my IP removed from the blacklist?
Since you are connecting through Comcast residential IP space, this restriction cannot by lifted at this time. Please see above instructions on "how to" options to send email without lifting this block.