Hello,
9.0.0-20 version is the first version of 9 series.
On 9 versions most important change is there are no Directory Syncronizations, now Brightmail rapidly access to Directory sources for checking something.
But on your version there are some problems about this new Directory Source technology.
On 9.0.2 they all fixed and now Brightmail working much steady.
Our so many customers in Turkey( some of over 20.000 clients) using 9.0.2 version and we have no problems about that.
So i think there's no problem to upgrade 9.02 version.
Regards,
Oykun