It appears that the forum is sending with a envelope-from domain of www1.camaro5.com which doesn't exist in DNS. 99% of spam filtering solutions out there just outright drop email with a non-resolving envelope-from domain because legitimate mail should be sent from a host that exists in DNS, and this would explain why email's not making it to a lot of people, myself included.
A quick solution would be to add an A record for www1.camaro5.com, since presently that doesn't resolve:
eldenser:~ jriley$ host www1.camaro5.com
Host www1.camaro5.com not found: 3(NXDOMAIN)
Also a likely contributor to issues once the forward DNS issue is fixed is the default reverse DNS record:
eldenser:~ jriley$ host 75.126.222.110
110.222.126.75.in-addr.arpa domain name pointer 75.126.222.110-static.reverse.softlayer.com.
That's going to score negatively on most spam filters as your from domain doesn't match up with your reverse DNS - would recommend changing it to www1.camaro5.com as well, which whoever owns the Softlayer account can do pretty easily in the SL control panel.
Current situation:
https://www.dropbox.com/s/66gss3emph...57.32.png?dl=0
Previously when email was being delivered to everyone your envelope-from was coming through as @camaro5.com, which exists in DNS:
https://www.dropbox.com/s/ovx2vaop5l...03.38.png?dl=0