Usually the best record creation follows the ID origin priorities, the best record is considering the data from the ID origin defined with the highest priority. In case 2 different ID origins are defined with the same priority, the latest import will be considered (technically identified via the latest ‘OriginDataLastChgUTCDateTime’). Communication data, such as email, mobile or phone IDs, however, consider marketing permissions as well. Any explicit opt-in given for a email, mobile or phone ID overrules the priority of the contact ID origin – an email ID with an explicit opt-in will be considered for the contact’s best record although it is coming from the origin data defined with a lower priority.
In addition the design might be influenced from BAdI CUAN_UPDATE_IC_ROOT ‘Update interaction contact (Best Record)’.