I just can't get a complete email setup to work, and I can't figure out why! Any and all help appreciated!

I'm running Debian ("unstable") on a linode 64. Here is some background info:
- relevant installed packages are exim4, uw-imapd-ssl, squirrelmail
- I first tried to install the imp3 package, but there was some kind of problem, so I removed that and installed it manually instead.

Stuff that works:
- I can mail out using the mail command (as in echo test | mail billl@example.com)
- I can read mail sent to my linode users via an external imap client (mozilla Thunderbird) (using ssl on port 993)
- I can log in on IMP and read email via imap (also using ssl, port 993)

Not working:
- I can't send email via IMP or Thunderbird. I get a "no relay" error in the exim logs, but I can't seem to find the setting to avoid this. I am using "localhost" to point to my smtp server in IMP. Why is this not working, while command line mail is?
- I can't even login to check my email on squirrelmail! I have run the squirrelmail-configure program, which seems straight-forward enough, but no luck.

Clues:
the command grep imap /etc/inetd.conf gives this result:
imap2 stream tcp nowait root /usr/sbin/tcpd /usr/sbin/imapd
imaps stream tcp nowait root /usr/sbin/tcpd /usr/sbin/imapd

cat /etc/pam.d/imap shows:
@include common-auth
@include common-account
@include common-session

The ssl certificate I'm using in imap is not officially signed, so to be able to login from IMP I have to specify the protocol as 'imap/ssl/novalidate-cert'. How do I do this in squirrelmail?

How do I setup exim4 to allow outgoing relay for all senders, using some kind of password authentication?

Thanks,

Robert

I got it working now, and I might as well document it here. Not that it's rocket science, but another email setup newbie might come along and read this...

What I've learned is for webmail clients (eg IMP) running on the same node as your smtp server (eg exim) you shouldn't configure the webmail client to use SMTP. Instead, you should specify it to use sendmail. Exim (and supposedly most other MTAs) includes a sendmail program which is a "sendmail compatible" front-end for the program. Using this, it's obvious for the MTA that the sender is local, and relay is not a problem.

Specifically, for my setup: all I needed to do was to add the line:
$conf['mailer']['type'] = 'sendmail';
at the end the file "conf.php"

That's it.