Check the timezone on your computer... while it might be showing the correct time, I think you will find the timezone is out those hours... Pacific time is my guess as that is the default of windows if it is not changed when the machine is first run.

My computer is set to the correct time zone and time. Other messages show correct times. My guess - and it's only speculation - is that the time displayed in the upper right is based on the *sender's* computer, and in the case I cited the sender's time was way off. If that's the case, my next question would be if it's possible to get the time displayed in the upper right to reflect either network time or the time on my computer.

I think I'm right. I deliberately mis-set my computer time, then sent an email to myself before setting it correctly again. Sure enough, the time in the upper right of the message as received was the bogus time. I note that there are two date/time column choices for the window that lists messages. "Received" shows the correct time; "Date" is the sender's (possibly bogus) time. So my question is now, is there a way to get the time displayed in the upper right of a message to be the "Received" rather than (apparently) the "Date" time?

I'm slowly getting more information. Apparently setting mailnews.use_received_date to "true" (which is what I had) is supposed to accomplish just what I wanted. However for some reason it no longer works - see https://bugzilla.mozilla.org/show_bug.cgi?id=607265. So now my questions have become: what setting, if anything, has taken its place, and if nothing, why?