So far, Zimbra has been working fine without any problem except the email receipt acknowledgement issue.
My next immediate task is to test out DimDim in Zimbra using the DimDim Zimlet.
I'm planning to migrate our students email system (about 8,000 users) from Openwebmail to Zimbra soon.
Thanks again to Zimbra for such a great software!!
Rgds;
Matnor