We are in the process of migrating from a simple Linux/Postfix/POP3 email server setup over to Zimbra (OSS, at least for now). As part of this migration we are trying to get as many users as possible to switch from Outlook to the Zimbra Web Client. We have four locations, and only one domain. The Zimbra server is located here at Corporate, and the three remote locations are connected up to this central server for email via a Frame-relay WAN.

One of the biggest complaints we have gotten so far from the users we have migrated over to Zimbra, especially from the remote locations, is the speed (or lack thereof) of the Zimbra Web Client. I think some of this is just users getting familiar with a new program, and new ways of doing things. However, I also have a feeling that the speed of our WAN may be a limiting factor.

So, based on this information I have a couple of questions. First, beyond the obvious of increasing our WAN links, is there any "performance tuning" that could be done to speed up Zimbra's response time? We are using https for the Web Client because we want to give the users the ability to connect up from outside our network, and obviously security is very important in this case. Is there any way to force secure connections remotely, but allow regular http connections internally?

Another thing I was thinking of was putting an additional server, or servers, at one or more of the remotes. I just started looking at the Multi-server documentation, and admittedly I have not read it in detail, but I'm not sure it covers my situation. I don't want multiple domains, and we're not trying to do replication or server load balancing. We would just want something where the servers at the remotes could potentially lessen the network overhead. Is this type of configuration possible with Zimbra?