Hi there,
as I recall you are using OL2010 in an enterprise environment? In many cases home directories etc. are residing then on network shares. And that’s where .pst files and .ost files most probably are being written, too. When profiles are being configured writing incoming mails to .pst files (so you have a "local" copy), you will run in a situation, MS does not support/recommend, as this slows down (yes, confirmed) the client and may have negative side effects to others on that share:
http://support.microsoft.com/kb/297019/en-us
Cheers Dirk
-- Dirk Jahnke-Zumbusch Deutsches Elektronen-Synchrotron DESY IT Information Fabrics Member of the Helmholtz Association D-22603 Hamburg Notkestrasse 85 / 22607 Hamburg