This solution applies to most Barracuda Networks appliances.
Navigate to Advanced > Troubleshooting and use the TCP Dump tool. Enter this command in the field and click Begin TCP Dump:
-e host <IP address of your workstation>
A pop-up window will appear with the output of the test.
Attempting 'tcpdump' ...The bold text in the output above is where you will find the MAC address of your Barracuda Networks product.
16:28:32.736103 0:1d:70:11:4b:47 0:19:db:6a:5b:cd ip 60: 10.2.63.6.4183 > barracuda.barracuda.com.8000: . ack 1219578298 win 65518 (DF)
16:28:32.736152 0:19:db:6a:5b:cd 0:1d:70:11:4b:47 ip 252: barracuda.barracuda.com.8000 > 10.2.63.6.4183: P 1:199(198) ack 0 win 6872 (DF)