I dug through the list archives and didn't see mention of this. If I set the synchronization mode for Inbox to "headers only", I run into a weird timing situation where when I try to download the message I get an error saying that the message is no longer available on the server. It is then marked as deleted and seen, and cannot be removed until I manually zap the message on the backend mail store. Logs of the sessions look completely normal, in fact, I can even see the offending message being fetched. I thought this might be due to "local customizations" to the server, but I was able to duplicate the issue with a stock version. I have duplicated this on two different machines, both running some flavor of Windows 2000, version 5.5 and 6 of OE.
To duplicate, send yourself a message, then click Send/Recv. The moment the message shows up, select it, and hit space or enter to download the message. Or just change the setting to download messages when selected. Timing seems important, since if you wait about 10 seconds or so, the message downloads fine. Just want to confirm that this is an OE oddity. TIA, Peter