We can SET this from control panel -> PORTAL settings -> Authentication -> LDAP -> How do users authenticate?. Here we can select whatever we require from email address,screen name or user ID. At the time of LDAP authentication, we need to PROVIDE the required LDAP mappings which basically reads all the details related to users and usergroups from LDAP directory and import into Liferay portal. At the time of this connection with THIRD party we need to give the required field like authentication should be by email address or screen name or user ID.

We can set this from control panel -> portal settings -> Authentication -> LDAP -> How do users authenticate?. Here we can select whatever we require from email address,screen name or user ID. At the time of LDAP authentication, we need to provide the required LDAP mappings which basically reads all the details related to users and usergroups from LDAP directory and import into Liferay portal. At the time of this connection with third party we need to give the required field like authentication should be by email address or screen name or user ID.