This article is for anyone who needs to reduce the mailbox size and to save a copy of backup.
It is applicable for MS Outlook 2013, MS Outlook 2016 and Outlook for O365.
Step 1: From the Inbox, select New Items > More Items > Outlook Data File
|Step 2: Select "Outlook data file (.pst)"||
Step 3: Select a location to store the pst file (recommended in ..\Documents\Outlook Files”
Step 4: Enter a File name
To add a password, check the “Add Optional Password” box.
Step 5: Select OK.
Type a password in both the Password and Verify Password text boxes and select OK again.
If you set a password, you must enter it every time that the data file is opened — for example, when Outlook starts or when you open the data file in Outlook.