This solution applies to the Barracuda Email Security Service.
You may receive this error when testing the connection to the Encryption Service from the IP Configuration page:
Loading encryption key...
Error performing SMTP test: Could't set FROM: 550 5.7.1 <encryption_test+119755+1307656151+0+RKflxF9ct ... 2zbE65w4epZi8fFFhs16uLY6fDlV5Aemail@example.com>: Sender address rejected: BAD SIGNATURE
This is due to the encryption key being incorrect. Please contact Barracuda Technical Support.