Donorbox uses email, first name and last name for matching with existing contacts in Salesforce. If one of these is not same, a new contact record is created. This leads to two cases:
1. If a matching email is found and either first name or last name is different, a new contact record is created under the existing account with the same email.
2. If the matching email is not found, a new contact record is created as a new account.