When a domain is added under Protocols > Domains, no event log is registered under the BCC admin event log or the Secure logs.
AuditEventLogManager: [-] Domain 'example.com' has been added by 'admin'
However, the domain entry can be found under domain.xml
<domain id='example.com' local='true'>
<recipientValidation enabled='false'/>
SMG 10.7.5
The Brightmail Admin Audit logs have been improved in 10.8.1 to include the addition, removal, and modification of domains from the Protocols > Domains list.