Got a response from Tony in support. Here's the somewhat edited response



I'm not sure what your setup is, but we were attempting to use a Barracuda Load Balancer which obviously won't work...

Thanks for the response - I'm going to open up a case with Zimbra on it and see what they say. Will post back if I get a resolution

Were you able to figure out what caused this? I'm having the same issue with our multi-server proxied setup. The second I enabled zimbraMailReferMode reverse-proxied we began seeing this.

If you...

Thanks for the response - we've opted to go with Ubuntu as well vs the appliance, mainly due to famliarity.

After talkign to some engineers at Zimbra we'll probably end up with a dedicated proxy,...

no suggestions?

We are in the process of planning a Zimbra 8 multi-tenant deployment. I've been reading the admin guide and it seems pretty straight forward, we will most likely separate the mailbox role from the...