Backup email in Outlook 2010
You can export your mailbox to a PST file to save a local copy of all your mails. To export, choose Export to a file option under the open menu of your Outlook file. Choose a .pst file under file types and click next.
Choose the items you want to export and check the ‘include subfolders’ box. Save your pst file at a chosen location and set a password to protect your pst file. This file can be accessed by file->open- >outlook data file.