[SGVLUG] email: Can I send it out directly?

[David Lawyer]

I think my email is working OK now, but I'm just curious about this.
Right now I use LA Freenet (LAFN) as my ISP and use their server to
send out my email.  This server is where my incoming email goes to
since I'm offline most of the time.  So it's clear that I have to use
POP or IMAP and get my email from them.

But what about my outgoing email?  When I dialup to my ISP use the
internet, I'm connected to the internet.  Exim (or sendmail, etc.)
could just send out my outgoing email to the Internet, bypassing the
mail server at LAFN.  I haven't set it up this way, but if I did, will
it work?

If I did this, my exim would first use DNS to find the mail servers
that I need to connect to and send packets to port 25 (ordinary email,
not TLS) on various mail servers.  If they accept my email, then I've
succeeded.  But will this work OK?  Will they accept mail from an IP
number that is roving (assigned to my isp)?  What if my email is not
accepted and returned to my temporary ip# just as I hang up my ppp
connection.  Then who gets the return packets?  Not me since I'm
offline.

And then what about authentication?  I suppose that it's only required
for relaying email and not if the mail server delivers mail locally to
the To: address ("envelope to" I suppose).  Of course, one reason for
sending outgoing email via your ISP's mail server is that you may not
have a program like sendmail installed that can use dns and send out
email directly.

As you can see, I don't know much about email servers although I
supposedly run one.  Per my logs, attempts have been made to relay
email from foreign countries thru my PC but it's been denied.

Don't spend any effort checking out my questions since I'm just
curious and don't really have any need to send email directly.  But I
was just wondering ...

			David Lawyer