Are you set up for local mail? Usually sendmail is set up to use mail or procmail as your local mailer and puts it into a file such as /var/spool/mail/username. If you want to be able to use a client to get it, you will need a pop3 server such as qpopper or you could use fetchmail. Both will poll the server and deliver the mail to your clients mailbox. Sorry I couldn't be of more help, but I don't know what you are running and how you set it up.