Received mail timestamp is off by 7 hours

[Pat Maddox]

I've been having a weird problem lately...when I download an email
from my mailserver, the time is off by 7 hours.  For example, if I
receive an email at 9:30pm, it lists the time as 2:30pm in my mail
client.  I've determined that it's just a problem on received
messages, because if I use my client with a different mail server, the
time is fine, and if I send mail to another server, the time is fine. 
It's annoying to me because messages will show up somewhere in the
middle of my 300+ message inbox, and users have been complaining about
it.  What's going on, and how do I fix it?  I'm using postfix and
courier-imap.