We have received reports from two resellers that Outlook users are experiencing connection issues. At this stage we are unable to recreate these problems, but beleive that it might be related to Zimbra Proxy - a service which we enabled some weeks ago and which manages the distribution of incoming connections to the appropriate backend mailbox server. We are currently running extended debug logging to attempt to identify this issue. In the mean time, please ensure that your users access via the correct server name as defined in the set-up instructions.