In my expierince, even though the online anti spam checks, are nice. They are not fool proof, the actual anti-spam companies like CloudMark, AT&T and others use thier own customized, and modified lists.
Which even in my experience, every half a year I have to write up a Anti-Spam request for whitelisting, the IT divisions, at these companies rather take an approach that is block all, ask questions later. If you are getting bounce backs, read the return email header information. They tell you where to go for removal, and how to contact them.
In my experience, CloudMark, and AT&T are the hardest to get removals from, It took me 4-5 requests, until I spammed AT&T’s Twitter account till they budged. CloudMark, needed a reminder. 90% of the time, these are form fill outs.
Find out who the anti-spam company/lists are they are causing your issues. Post them here, and it will likely go away soon after.