iRedmail 0.8.6 Installation Problem with Ubuntu 12.04 (LTS)

Hello All,

i have a VPS with Ubuntu 12.04.3 LTS installed. My system is up-to-date. Now i want to run a mail server in this. so i've choose iRedmail as it's one of the easiest tool to setup mail server. i've downloaded iRedmail version 0.8.6 (latest) and followed the instruction for ubuntu. But i ended-up with problem while installing--

i gave the command:

# sh iRedmail.sh

but i got the following error:

iRedMail.sh: 28: [: X1: unexpected operator
iRedMail.sh: 65: [: X127.0.0.1: unexpected operator
iRedMail.sh: 157: [: Xxterm: unexpected operator
iRedMail.sh: 168: [: XLINUX: unexpected operator
iRedMail.sh: 214: [: XLINUX: unexpected operator
iRedMail.sh: 313: [: XLINUX: unexpected operator
iRedMail.sh: 326: [: XLINUX: unexpected operator
Error: Your OS is not supported yet.

i can't understand why my OS is not supported?! it's Ubuntu 12.04 and it supposed to work fine, any idea? plz anybody help me here.

Regards.