I came across this in an article that may help:
"Try to enable only the headers
By default, Outlook 2010 downloads both the emails and the attachments for every folder. As a result, users with mailboxes larger than 1 GB may find that Outlook takes a long time to download their messages. Previous versions of Outlook only downloaded the message headers by default. This setting was changed in Outlook 2010 to allow the program to index all content and display information about the emails and attachments each contact has sent Follow these steps to change this setting to only download the message headers to speed up Outlook:
Run Outlook 2010. Click the Send/Receive tab. Click Send/Receive Groups and select Define Send.Receive Groups.
This will allow you to edit settings for send/receive groups.
Select All Accounts and click Edit. Click the Download headers for subscribed folders option. Click OK. Click Close. "