If any of the computers in your organization get infected with a botnet or other malware, it can send out spam emails, thereby possibly landing your domain(s) or IP address(es) on a blocklist, not to mention spreading the malware. Use the BLOCK/ACCEPT > Sender Filters page to control which domains and email addresses can send email out through the Barracuda Email Security Gateway. Note that both inbound and outbound email messages from whitelisted ("allowed") domains/subdomains bypass spam scoring as well as all other blocklists, but do go through virus checks.
Email addressed from specified email addresses and domains/subdomains can also be encrypted or redirected from the BLOCK/ACCEPT > Sender Filters page.
Outbound email addressed to specified email addresses (recipients) or domains/subdomains can also be allowed, blocked, encrypted or redirected from the BLOCK/ACCEPT > Recipient Filters page.
For more information about email encryption and redirection, see Encryption of Outbound Mail 6 and Above.