Hi all, I have one client which they have about 700 users and everyone uses online mode. Their mailboxes get bigger and bigger and also no limit on anything (political resason). Now, they complaint it takes a while to open mailboxes. I try to ask them to use the cache mode. Most users are using outlook 2003 and some use outlook 2007. Will cache mode help them in this situation? (windows 2003 SP2 and Exchange 2003 SP2) Thank you.

Yes, however for extremely large mailboxes upgrading to Outlook 2010 will provide much better performance in cached mode.

Just how big are these mailboxes? I've only started working with Exchange 2007 but it seems to me that your total mailbox DB size could only get so big with Exchange 2003 - 75 GB it seems (maybe more with Enterprise?). Otherwise, cache mode should limit the work load on the servers, since much (or most) of the data will be accessed locally (in the .ost file). That, in turn, may affect access time favorably. Most often, cache mode is preferred, with some exceptions (it can cause sync problems for Blackberry users if I recall correctly). Other factors may come into play, so you'd have to try, perhaps with a subset of users, and see what happens.

In general it should, and It really isn’t the size of the mailbox rather other factors will cause the performance issues and you may need to look deeper into current situation to develop better or permanent remedy. Here are some tips to look more into…. The most obvious one is to upgrade Exchange Server latest greatest E210, ( the most advance faster lighter Exchange version is E210). Upgrade Clients Outlook to Outlook 2010, and look over bandwidth usage utilization avoid un-necessary deployments ( VPN for outlook etc) Plan an Exchange deployment in Outlook 2010 http://msexchangeteam.com/archive/2007/12/17/447750.aspx Outlook users experience poor performance when they work with a folder that contains many items on a server that is running Exchange Server http://support.microsoft.com/kb/905803 setting Up Outlook 2003 Cached Exchange Mode Accounts http://office.microsoft.com/en-us/office-2003-resource-kit/setting-up-outlook-2003-cached-exchange-mode-accounts-HA001140259.aspx good luck ocd Oz Casey, Dedeal MVP (Exchange) MCITP (EMA), MCITP (SA) MCSE 2003, M+, S+, MCDST Security+, Project +, Server + Http://smtp25.blogspot.com (Blog Http://telnet25.spaces.live.com (Blog) Http://telnet25.wordpress.com (Blog)