I am attempting to send some emails through my ISP (Comcast) via sendmail on my FC3 machine.

I have managed to successfully create a Comcast email address and a corresponding local user name (Example: admin@comcast.net and a user account called 'admin' on my Linux machine).

Here's my problem:

I can create an alias in the /etc/aliases file that automatically sends local mail to admin@comcast.net, but since sendmail expands aliases, if the "terminal originator" of the message is, for example 'root,' the mail is undeliverable because there is no Comcast account called 'root@comcast.net.'

So my question is, how can I make it so that any system processes that run as root (and consequently send alert emails as root) will be able to send mail out using that 'admin' account that DOES have a corresponding Comcast email address?

I'm sorry, I know this is very convoluted, if you need clarification, please ask.

Thanks.

I think what you want to do is alias the root user to admin - in /etc/aliases add:
root:admin

Then run newaliases.

the problem is when I create the alias root:admin, it resolves to root@comcast.net when it sends to Comcast's smtp server. Since root@comcast.net doesn't exist (at least it's not assigned to me), the message gets returned

If I understand your problem correctly, you are wanting to re-write the from address to match that of your comcast account. If thats the case, then take a look at http://www.infohiiway.com/sendmail/#two

In particular, the per-user solution.

I got it to work. The "per-user" method did not work, but the "systemwide" method did.

Thanks a lot!