Many have found that an effective way to improve the accuracy of their Barracuda spam filter is to use SpamHero in front of their Barracuda appliance. In addition, if your Barracuda goes down, SpamHero will hold your mail until it is back online.
Here are the steps required to combine SpamHero filtering with a Barracuda's appliance:
According to Barracuda's website, here is how to whitelist the SpamHero IPs:
"To exempt an IP address from RBL scanning go to the Block/Accept > IP Reputation page, and enter in the IP address that you would like to exempt from RBL checks. Any IP address or IP range entered here will be skipped when scanning incoming mail against any RBLs configured on the Barracuda Spam Firewall." For the full article, see: Dealing with Barracuda Reputation (RBL) False Positives
Be sure to include all IPs listed on the Current List of SpamHero IP's.