Weird inbox selection behavior in Mail

[Steven Rogers]

I've noticed that certain messages in my inbox will cause the message 
selection to change when there's an event, such as auto-checking the 
mail. It causes the selected message to jump forward to them in a batch 
of new mail. If one is selected when mail is read, then it becomes 
deselected.  I can't figure out what the message have in common except 
that they are all routed through the same SMTP server which is an 
IPSwitch brand IMail server. There are no unusual header lines in the 
messages, and the mail is being composed in a variety of programs 
(Eudora and Outlook) so I can't even guess what might cause the 
behavior. Anyone else seen this? Deleting the message causes the inbox 
selected message behavior to return to normal.

Steve