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:

1. Configure your MX records to point to SpamHero as usual.
2. Enter the host name or IP address of your Barracuda appliance as the delivery host on the Settings > mail host tab in SpamHero.  Very important:  On the same page, you must use the Dedicated mail host option so that SpamHero will send your mail from a static list of IPs:

3. You will also need to whitelist our IP addresses to prevent Barracuda's over zealous RBL from blocking our IPs. The list of IPs to whitelist are found here:

Current List of SpamHero IP's

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.