I have the same problem. SYMANTEC BRIGHTMAIL isn't great of late. It is blocking a whole /23 of IPs that were on the Spamhaus PBL weeks ago that we now are using on dedicated hosting servers for email. They aren't on ANY other blocklists at all. We manage the list there and removed them ourselves, and the only reason we put it there is because it was assigned to dynamic users. Well that is months ago, and Symantech doesn't update there list. It keeps getting blocked constantly. We are daily removing them.
I have the following impressions so far:
Noone reads the reason on the email, or there is a robot skipping it.
There service is on par with the pay to remove blacklists.
My customer service requests and problems are not being responded to.
We actually contacted Spamhaus about the issue, and they even weren't keen on the fact that it was still being blocked as a reason because of them, when it clearly had been removed weeks prior.