I'm using scalix with 20 premium accounts conecting to scalix from outlook via scalix connector.
When lunching outlook it is almost (95% of tries on some machines) certain that it will stop responding when it tries to send/recive emails when the smartcache synchronizes. Even if the smartcache stops synchronizing outlook wont respond any more - it like its still waiting for scalix server to respond - on the outlook tray icone I get a message like this "if you trying to connect to exchange server, click on the tray icon to cancel connection" (a very loose translation) but there is no option to do that. The outlook tray icone is then in most cases not the orange one but white with two emails.
Only way to resolve the issue is to kill outlook, wait to smartcache to synch, and then tray again (helps after 5-10 tries) or to stop outlook from reciving emails - but you have to make it before its to late, and its not that easy sometimes.