EmailDLL Online Manual
Returns: Success or Error Status
This method deletes all currently assigned recipients of the email message. These are the addresses that were in the To: header field, which were set with the Email.AddRecipient() method.
While it is certainly safer to call this method, it is not really necessary to do so unless you are sending more than one email message with a single Email class. Unless, of course, you have other reasons for doing so.