I did exactly as you recommended, and split the original CSV file into smaller files via Excel, and then attempted to import each file separately. I received the same error message at each attempt:
The format of the CSV file isn't correct. Please be sure that the file was exported in the Outlook CSV format.
Once again, the individual 3 files, created by me in Excel, as a result of manually splitting the original CSV file, were named:
aa-yahoo_contacts.csv
ab-yahoo_contacts.csv
ac-yahoo_contacts.csv
Will you please help me solve this problem? Thank you in advance.