[Exim] Problems with netscape6 and mailscanner

I keep getting an error using netscape6 email on my solaris
2.8 running exim 4.04 with mailscanner 3.13...
..the error when I send email is :

     'An error occurred while sending mail.
     The mail server responded :
     Unexpected failure, please try later.
     Please verify that your email address is correct
     in your mail preferences and try again'

   the only setting I've changed on my mail account in netscape6
   is 'My Outgoing Server (SMTP): mancity:sghsms.ac.uk' - my local unix
        box from 'mail.sghms.ac.uk' - the mail server..

    mancity is the host with mailscanner/exim running on it..

the screen freezes and no email is sent...?

BUT if I use /usr/lib/sendmail -v username@??? as root
the user recieves the email..?

    ..Any suggestions would be much appreciated...?
--
   Asim Khan
   Unix System Administrator
   Computing Services
   St George's Hospital Medical School
   Tel: 020 8725 5453