MIME gone bad!

For a while now I've been having a problem with my 7.0.3 Domino server running Symantec Mail Security queuing messages in its mail.box(s) for hours on end before finally delivering them at some point during the day. The messages appeared to be spam in nature and really didn't think too much about it until recently when I've been noticing a lot MORE messages getting stuck there for hours on end. So, it was time for some troubleshooting.
Looking at the messages that were hung up, I could see that they were MIME messages, but that was really about the only thing I could figure out about them. Nothing too special about them at all.
As I was sharing this information with a colleague of mine, she told me that at her former place of employment, they were having the exact same issues with the two products as well. That's when I decided that it wasn't something I did, but it appeared to be a shared problem. So back to the document properties of the stalled messages and the SAV log I went to look for clues. That's when I found the key to the whole problem. From what I've seen over the years in the SAV log, Symantec has never been really good at handling MIME based messages, usually spitting up errors like:
One or more components could not be scanned due to scan error (Unable to open container) from mime.txt.
I then figured that when this occurs, either Symantec or Domino changes the delivery priority of the message from Normal to Low since the messages pending had the DeliveryPriority value set to L. Finding the solution to the issue now was pretty straight forward. Since Domino is very good at doing what it is told, I looked into the configuration for the server under Router/SMTP-Restrictions and Controls-Transfer Controls. The field for Low priority mail routing time range: was set to the default of 12:00 AM - 6:00 AM. So any of those messages that were sitting there would be delivered between that time. I changed that setting to 12:00 AM - 11:59 PM, saved and closed the document, waited a few minutes, and the messages had magically disappeared. So somewhere along the line, bad MIME was causing the priority to be changed and the messages queued. Not sure at what process it was that was causing the issue, but for now I know at least that 1.) I'm not crazy and 2.)The issue is resolved.
Weird.