When importing data into SugarCRM using Starfish, users will generally want to disable the Assignment Notification functionality in the Admin -> Email Settings area of SugarCRM.
If importing many thousands of records, you would not want the system sending out many thousands of emails each time a new record is created. In addition, the process of sending out emails can slow down the import. This is especially true if the Email Settings are not setup properly. Many thousands of errors will be logged to the System Log and slow the import down even more than normal.