Entourage problems due to entourage timeout sensitivity
Regarding your problem with Entrourage users not getting their mail -- this behavior happened even with legitimate MS Exchange servers. Entourage was simply too picky about timelyness of responses, stopping communication even if the SSL session was still up in the event the server didn't respond with 500 ms or so (that's half a second!). Microsoft reduced the problem it in the most recent Entourage 2004 update, but they still haven't fixed it completely. If Entourage doesn't get an answer to an SSL subquery within a couple of seconds, it goes brain dead and won't communicated anymore. You must relaunch Entourage to get arround this.