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. From the Folder menu click the AutoArchive Settings button.
Select Archive items in this folder using the default settings. Next click the Default Archive Settings button.
Check Run AutoArchive every... (you set the number of days, default is 14). Uncheck the Delete expired items (e-mail folders only) checkbox. Finally make sure that the Permanently delete old items radio button is not selected.