Step - 1. On the File menu, click Import and Export.
Step - 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. 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.
Step - 5. Under Save exported file as, click Browse, and then specify a name and location for your backup file, (for example, Mail Backup).
Step - 6. If you back up a .pst file that you have backed up to before,
Click one of the following:
Replace duplicates with items exported: Existing data will be overwritten with the
information in the file being exported.
Allow duplicate items to be created: Existing data will not be overwritten, and duplicate
information will be added to the backup file.
Do not export duplicate items:
Existing data will be kept, and the duplicate information in the folder will not be copied
to the backup file.
Step - 7. Click Finish.