I'm installing Zimbra on a local ubuntu server.

-OS: Ubuntu 7.10 (Gutsy Gibbon)
-Here is the tutorial I'm using:
How To Install Zimbra Collaboration Suite (ZCS) On Ubuntu | HowtoForge - Linux Howtos and Tutorials

-Here's the output:
chown: `zimbra:zimbra': invalid user

Operations logged to /tmp/install.log.5182
Checking for existing installation...
zimbra-ldap...NOT FOUND
zimbra-logger...NOT FOUND
zimbra-mta...NOT FOUND
zimbra-snmp...NOT FOUND
zimbra-store...NOT FOUND
zimbra-apache...NOT FOUND
zimbra-spell...NOT FOUND
zimbra-core...NOT FOUND
./util/utilfunc.sh: line 457: rpm: command not found


PLEASE READ THIS AGREEMENT CAREFULLY BEFORE USING THE SOFTWARE.
ZIMBRA, INC. ("ZIMBRA") WILL ONLY LICENSE THIS SOFTWARE TO YOU IF YOU
FIRST ACCEPT THE TERMS OF THIS AGREEMENT. BY DOWNLOADING OR INSTALLING
THE SOFTWARE, OR USING THE PRODUCT, YOU ARE CONSENTING TO BE BOUND BY
THIS AGREEMENT. IF YOU DO NOT AGREE TO ALL OF THE TERMS OF THIS
AGREEMENT, THEN DO NOT DOWNLOAD, INSTALL OR USE THE PRODUCT.

License Terms for the Zimbra Collaboration Suite:
http://www.zimbra.com/license/zimbra..._eula_2.1.html


Press Return to continue

Checking for prerequisites...
NPTL...FOUND
sudo...MISSING
libidn...MISSING
curl...MISSING
fetchmail...MISSING
gmp...MISSING
/usr/lib/libstdc++.so.5...MISSING

###ERROR###

One or more prerequisite packages are missing.
Please install them before running this installer.

Installation cancelled.

- I've installed all of the prerequisites per the tutorial and everything went smooth.

I would really appreciate any help!