Configuring host (for mail)

I downloaded pine, so i can use text email (or so i thought)

i tried sending out a test email, but it came back bad because my sender email did not exist... anyone know how i can correct this:

----- Transcript of session follows -----
... while talking to po0.wam.umd.edu.:
>>> MAIL From:<justin@localhost.localdomain> SIZE=474
<<< 501 <justin@localhost.localdomain>... Sender domain must exist
501 5.6.0 Data format error

[ Part 2: "Delivery Status" ]

Reporting-MTA: dns; localhost.localdomain
Received-From-MTA: DNS; localhost.localdomain
Arrival-Date: Wed, 30 Jul 2003 16:11:36 -0400

Final-Recipient: RFC822; jstahler@wam.umd.edu
Action: failed
Status: 5.5.2
Diagnostic-Code: SMTP; 501 <justin@localhost.localdomain>... Sender domain must exist
Last-Attempt-Date: Wed, 30 Jul 2003 16:11:53 -0400


[ Part 3: "Included Message" ]

Date: Wed, 30 Jul 2003 16:11:32 -0400 (EDT)
From: justin@localhost.localdomain
To: jstahler@wam.umd.edu
Subject: test back


Thanks,

Justin

I am just curious. Are you able to ping any outside servers like Yahoo or Google? Type in

ping http://www.yahoo.com
ping http://www.google.com

and see if that works.

indeed, i can ping them... I have a few domains hosting off my box also, everything seems to be working well (of course excluding the mysql php nightmare ihave been having)

my server name is just called local host at localdomain, and i dont know how i woudl change that...

thx J