Step 1a: Outlook 2010 - Click the File Tab, click Open, click Import.
Step 1b: Outlook 2007 - On the File menu, click Import and Export.
Step 2: 2. Click Export to a file, and then click Next.
Step 3: In the list, click Personal Folder File (.pst), and then click Next.
Step 4: 4. Click the folder that contains the messages you want to back up. If the folder contains a subfolder that you want to include, select the Include Subfolders check box, and then click Next.
Note: if you want to export the entire mailbox, make sure you select “Mailbox – Your Name” for 2007 or Your email address for Outlook 2010 and make sure Include subfolders is selected.
Step 5: Under Save exported file as, click Browse, and then specify a name and location for your backup file, for example, Mail Backup.
If you back up a .pst file that you have backed up to before, click one of the following:
Step 1a: Outlook 2011 - On the File menu, click Export.
Step 2: Select your export options.
Step 3: Select the option “No, do not delete items”
Step 4: 4. Type a name that is suitable for the backup file in the Save As: box, and select a location where you can easily find your exported file.
Step 5: 5. You’re all done. Click the Done button to complete the export process.