Upgrade 4.11 to 5.x

[newmember]

I have been unsuccessfully been able to upgrade from 4.11 to 5.x many many times. I keep having postfix errors.
I am thinking that I want to do a fresh install of 5.x (prefer 5.06_GA) and move all the accounts and emails instead of upgrading. Is there a guide on how to do that? Maybe I need to use imapsync?

Thanks

[newmember]

This might be considered as moving zimbra from one OS to another OS.