We have been using Zimbra Open Source for the last 6-7 months, and so far it is way, way better than the previous Exchange server we had.
Everything worked really really great, until we needed to turn the IMAP proxy on, so our SugarCRM installation could download our user's email boxes.
When I turn the proxy on, the Zimbra server starts using all the resources until it reaches 100% (RAM, processors) and it becomes really slow.
I looked in the forums but didn't find anything, any ideas?
By the way, if it helps, it is running in a VM under VmWare ESXi 3.5 U4, 4 GB Ram, 500 GB hard disk, 2 processors assigned.