If you are receiving errors about being close to your quota for your Exchange e-mail account, you should consider archiving your older messages. Archiving copies old e-mail messages and attachments to an Archive.pst file (you can change the name during with the manual export process) and then removes the data from the Exchange mailbox decreasing its overall size. Items moved to an Archive.pst file are still accessible by opening the file through Outlook, and should be included in regular backups to prevent lost data. If you need more assistance in managing your mailbox size, see the Quota Management page for Outlook 2010.
Open Microsoft Outlook. Click the Tools menu at the top of the the window and then click the Mailbox Cleanup... menu option.
Click the AutoArchive button to archive the older items to your computer and remove them from your Exchange folders.
After archiving the items, the items can be found under the Archive Folders underneath the Mailbox folder section.