imessage for mac mini

Probably because they are running different OS X versions.

Click on "Apple > About This Mac" and check both machines.

Unless the Mini were very old, you can install 10.8.2 on it as well. Go to the App Store and shop for Mountain Lion.

I did install the latest 10.8.2.

I am assuming my MAC Mini is old (about 1½ year) . Is there a way to check if Apple has stoppped supporting older mac mini? How do i know if i have an older mac?

Well, if you have 10.8.2, you do have Messages = iMessages. Under preferences you can activate an account and one or more email addresses under which you can be reached.

1.5 years is not too old for 10.8.2, and the fact that you were able to install it is proof. According to the following links a Mini compatible with Mountain Lion must be the 3,1 model or newer, or from early 2009 or later.

http://www.apple.com/osx/specs/

http://discussions.apple.com/docs/DOC-3761

To find out what your Mac is, click on the apple in the upper left corner, then "About This Mac". "More Info" gives you exactly that, and in "System Report..." you'll see all details.

Thank you for your response. I was able to configure the preferences. thanks