Had a situation that I thought would be of interest to some folks now and in the future.
We had the Local Deliver building up a queue that wasn't going anywhere over a period of some hours. The message at the top of the queue didn't look "bad" or spammy but it wasn't going anywhere. Viewed the queue with "omstat -q local".
Stopped Local Delivery but it showed partially aborted instead of shutting down cleanly. Then I found I could not find the message on the queue at all. Thought that a bit strange. Happened to check the 'top' and found two processes belonging to Scalix consuming huge resources like 40% CPU each, sometimes it went higher. Decided to stop Scalix and restart, thinking it should be clean but as soon as it restarted these two processes started up as well. Local Delivery would empty it's queue out eventually but then after a time it would start to build up again. Also found after a couple of restarts of Local Delivery that there were more of these processes.
Eventually I stopped Scalix and killed off the two processes that were taking up so much CPU. When I restarted Scalix these two processes started up again this time I killed the two processes whilst Scalix was running. It appeared to fix the problem. They did not come back and after the next restart they didn't return either.
Since then have found out that these two processes are called by Local Delivery to handle incoming messages that require formatting from rtf to html. Not sure what triggers this though? The message that it appeared to be dealing with in my case was a 100MB file that was really junk mail as it turned out, not something critical.
There is a file that is created in the ~/temp directory with a ".rtf" at the end of it that will give you some indication of what is being converted. Although in our case this file was huge so didn't go through all of it to find out who the message was for or from but could see some of the content.
Just an FYI in case anyone else comes up against this. Maybe others have delved further into this process and can add info?