arj267,
Please continue to forward messages where you get this error to thisisnotspam@cox.net so the spam filter can learn more about your messages. There is something within the message itself which is triggering the filter. It could be a link, an attachment or the fact that it originated as a bulk email. If you're forwarding and the message is expanding a list of recipients in the forward you can try removing the addresses.
Adittionally, if you are trying to forward the message to multiple recipients, try reducing the number of email addresses you are forwarding to.