Moving from Ubuntu 6.06 to Debian 4

[azeem]

I'm currently running Zimbra OSS 4.5.5 on Ubuntu 6.06 on VMWare. Since my VM only has 8 GB of diskspace I haven't been able to upgrade to a newer version of Zimbra.

Now, I have new hardware, with XenSource virtualization, and I'm planning a move to new hardware, new Virualization software, and new OS.

I have studied most of the Zimbra migration guides and posts, and I understand that i have to migrate to the same version of Zimbra, namely 4.5.5. However, I'm unable to find this old version of Zimbra as a download. I have 4.5.9 and 4.5.11 downloaded, but can't find 4.5.5 anywhere.

How do I go about my migration now? Where can I find 4.5.5?
Appreciate any hints on my particular migration as well.