Exchange 207 DST Problem

Hy all,
I have a problem on exchange 2007 sp1 handling time. Eventhough, The Middle Eastern time (GMT+2 with DLS) is correctly set on all servers/workstations,when an appointment is received through smtp/pop3 account the schedule is always 1 hour late (when received with exchange account the appointment time id fine). All workstations have xp and office 2007 with all updates installed.
Any help is highly appreciated
Regards,