Problem install postfix part (7.10) on ubuntu hardy

[DefZero]

Hi all,
My first post,

I'm trying to install ISPConfig on an Hardy system. I've used the installation guide "ISP Server Setup with Ubuntu 7.10 (Gutsy Gibbon)", untill page 5 no problems there, but when i try to execute the line

apt-get install postfix libsasl2-2 sasl2-bin libsasl2-modules libdb3-util procmail

I get an error:

"
apt-get install postfix libsasl2-2 sasl2-bin libsasl2-modules libdb3-util procmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
libsasl2-2 is already the newest version.
libsasl2-modules is already the newest version.
E: Couldn't find package libdb3-util
"

Is there way arround this problem?
Can i use the package from 7.10, or should i use the packages only from hardy(that is what i preferre), is there a different howto i can use for this postfix part.

Thanx in advance,

Hans