Microsoft Outlook 2010 is running too slow.
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: