Advanced Authentication validates the specified attributes for an entered user name.
For Active Directory (AD), the default attributes are sAMAccountName and userPrincipalName. For other repositories, cn is the default attribute.
NOTE:Points to consider about the otherMailbox attribute:
Advanced Authentication 6.4 Service Pack 2 Patch 1 includes the otherMailbox attribute as default attribute in User lookup attributes.
When you upgrade to Advanced Authentication 6.4 Service Pack 3 then the otherMailbox attribute is supported as default attribute in the existing repository. However, for a new repository, the otherMailbox attribute is not supported as default to improve search and performance.