Sendmail/Linux Help

[Eric F Crist <mnslinky@eua.tzo.org>]

Hey,

My web server got hacked on Thursday.  I had to do a complete reinstall due to
the fact that shadow/password and init files were deleted.

Since I reinstalled linux, sendmail doesn't recognize any users.
I can send mail from localhost to any users, but I can't send mail to
myemail@<myhost.com>, as I get errors 550 (Relaying not allowed) and 551
(Unknown user)

The other problem:

Ever since I installed linux, new users show up unexpectedly.  For example,
It's like someone is going into my server and creating accounts with names like
reboot, system (UID 0, GRP 0), and other accounts that look legit, but I know
they're not (Caldera, by default, enters Caldera OpenLinux User in the Name
field, Unless you change it manually).

Can someone please help me?

I don't understand ipchains, and I need help setting up as a gateway.

I also need to know how to setup sendmail so that it'll accept the correct
accounts (note: it won't even accept mail for root, postmaster, and
MAILER-DAEMON)

If you would like to see the error message, send an email to
ecrist@ardent-hacker.net. (This is the account I am logged in as usually)

Thanks

Eric F Crist