I've installed Tiger on two machines, an iBook and a PowerBook G4. In both cases the timestamp on incoming POP server mail is recorded in GMT, rather than my local timezone (EST). I've found a workaround -- listing mail by date sent, rather than date received -- but it irks me that the problem...
This is a known problem in Tiger Mail: the app shows Date Received in GMT time, although Date Sent and the mail itself shows the correct local time.
Workaround: hide Date Received and show Date Sent.
Meanwhile, eager to hear if anyone has found a fix.