I believe that Panther was querying you on which one you were trying to do so that they knew more about what you were tryign to do since you stated that it gave the error of "your default mail client is not properly installed". This generally indicates that you are trying to send it from somewhere other than a server that has mail. If you are sending from soewhere that doesn't have mail server access wether it be QMail, SendMail, or some other form of mail, even the PHP mail() call to call the mail server set in the PHP.ini, then it won't be able to send the email.
So please let us know where oyu are attempting to send it from at this time so that we can better assist you.