In this mode, new contacts will be inserted into Front and existing contacts will be updated.
User Identification
To determine whether a contact should be created or updated, you will need to provide a column mapping that can be associated with a unique Handle in Front.
A user can have multiple handles but we will only use one to determine the existence of a contact in Front. Please provide this mapping in this section of the sync configuration:
Please ensure that the column you are mapping to is unique and non-null. Also
keep in mind that making changes to this mapping later on can result in
unexpected behavior.