I am running a debian box with a dial-up connection. I would like to set it up so that it can send mail directly to the outside, without using a smarthost. I need it so I can make use of a php mailing script that I have. What do I need to set this up?

I was trying to use exim, but I couldn't get mail sent with php. I am able to telnet to port 25 and mail users locally, but if I try to send to an outside email, it just says "550 unknown user". I am running exim4. Also, what should I put in the php.ini file for the path to the SMTP server? I put /usr/sbin/sendmail (which points to exim4), but without options it just spits out some text to the console.

I've looked around for help on this, but I haven't found much yet. Thanks.