Typically, when Comcast blocks an IP address from sending email into their network, they will not provide detailed information on why the block was put in place. The bounced error message from email sent from an AIT server to a Comcast email account reads as this:
Failed to deliver to ‘user@comcast.net’
SMTP module(domain comcast.net) reports:
return-path address 550 66.118.148.16 blocked by ldap:ou=rblmx,dc=comcast,dc=net BL004
Blocked for spam. Please see
//www.comcast.net/help/faq/index.jsp?faq=SecurityMail
This means that Comcast has blocked an AIT owned IP address.
To get this IP unblocked, AIT recommends that Comcast subscribers, who also may be AIT customers, should alert the Comcast technical support that they have a web hosting account with AIT, a Comcast internet access account and Comcast is blocking email between the two. Typically, this will expedite the removal of the block because there is a financial commitment between the Comcast customer and Comcast.
While AIT has an Abuse Department to attempt to address these problems, communication with Comcast’s abuse side is email only and AIT has had difficulty removing the blocks in a timely manner. The URL below is the page that is used to communicate with Comcast regarding a block such as this.
//www.comcast.net/help/faq/index.jsp?faq=SecurityMail_Policy18628