SecurityEdge Blocking Certain Email Domains

I am having specific domains blocked by Comcast security software and emails from these domains are being pushed into Comcast's spam folder.  I have spoken to support multiple times and they have no solution other than for me to tell the company sending emails to check their email reputation.  I was told they turned off SecurityEdge as that should fix the issue, but no change.  Also, I know they are using third party companies to evaluate emails coming into their servers of which their customers have no control over.  I spoke to Akamai and they validated that they are working with Comcast with regards to security, but could not divulge any further details.  I suspect that their might be other companies as well from reading past posts, but I have no way of verifying this as Comcast will not release this information.  Akamai could look into my issue, but they would need Comcast to initiate this, which at this time they won't.  We have set up filters to allow specific domains being blocked to pass through, but that has no effect either.  Their email support person was not at all sympathetic to our situation and he only offered one resolution and that was to tell our vendor to check their email reputation not how to let specific domains pass through.  I asked him what good are the filters if they have no affect on permitting specific domains to pass through.  He had no answer.  As a business my IT should have control over what emails should and should not reach my network, not Comcast or their third party's software.  Very disappointed!