Nothing fancy here, I just need sendmail to be able to send messages out to the internet from my redhat 9 workstation. I'm not trying to run a mailserver or anything.

It's fresh off the install, and I haven't edited any sendmail config files (because I don't know how or which ones to edit). Here's what I get back when I try and send an email:

----- Transcript of session follows -----
... while talking to flmx04.mgw.rr.com.:
>>> MAIL From:<root@localhost.localdomain> SIZE=328
<<< 553 5.1.8 <root@localhost.localdomain>... Domain of sender address root@localhost.localdomain does not exist
501 5.6.0 Data format error

--h9UDR1dx005841.1067520421/localhost.localdomain
Content-Type: message/delivery-status

Reporting-MTA: dns; localhost.localdomain
Received-From-MTA: DNS; localhost.localdomain
Arrival-Date: Thu, 30 Oct 2003 08:26:10 -0500

Final-Recipient: RFC822; edited.email@address.com
Action: failed
Status: 5.1.8
Diagnostic-Code: SMTP; 553 5.1.8 <root@localhost.localdomain>... Domain of sender address root@localhost.localdomain does not exist
Last-Attempt-Date: Thu, 30 Oct 2003 08:27:01 -0500

So, let me get this straight, you haven't touched anything yet to get this working? What about read any sendmail docs? That would be the first place to start. Something of this caliber requires correct configuration inorder to work properly.

That's right, I haven't touched anything. I've read a large amount of documentation (enough to know that I shouldn't touch anything because I don't know how!). I'm almost certain that for my simple task, there's a simple solution. I just need to know how to send a message to an internet address using sendmail.

I'm pretty sure I can achieve this by editing some file to reflect my actual ISP instead of localhost.localdomain. But which file? And what is m4? I read that I should edit that file, but what parts?

See, I need help..

m4 is macro to change the sendmail.mc into sendmail.cf.
try to masquarade it to your isp. in line like MASQUERADE ?
maybe you can try to found some usefull informations in hhtp://www.tldp.org and search it for sendmail how to

turns out all I needed to do was add an entry in my /etc/hosts file to reflect my ip address and a fake domain. i.e.

127.0.0.1 locahost.localdomain localhost
192.168.0.1 server.mydomain.com server

Then I rebooted and voila, it worked. The problem was that the ISPs were bouncing my emails back because they won't take any mail from the localhost.localdomain domain.