With lots of email coming in to our mailboxes daily, surely you will need to backup your Outlook files. 


File> Open> Import>Import and Export> Export to a File>Outlook Data File (.pst) 


In the 'Select the folder to export from' list, select the folder to export 
- Inbox, Sent Items, Drafts, Contacts, Conversation History (MOC/Lync), Journal, Notes, Calendar, Tasks. 
- Make sure you select 'Include subfolders' if you want to backup all subfolders. 


How to Restore Outlook Files 

File> Open> Import>Import and Export>Import from another program or file

Outlook Data File (.pst)> Browse for the file to .pst file to be imported and choose the following Options: 

* Replace duplicates with items imported
* Allow duplicates to be created
* Do not import duplicates


Outlook .pst or .ost file and what are they different from each other?
 
Outlook uses 2 types of Data Files, they are Outlook Data File (.pst) if you are using Microsoft Exchange Account where your items are usually delivered to and saved on the Exchange server and the other is called (.ost) file which enable you to work with your email messages even when you are not connected to the Exchange server. 

(.pst) Outlook Data File - used for POP3, IMAP, web-based email accounts, Exchange accounts to create archives or backup of Outlook Folders and other items. 
 
- Regular backup of .pst file to a safe place is recommended. 


Location of .pst file

Windows 7 and Windows Vista    drive:\Users\user\AppData\Local\Microsoft\Outlook

Windows XP     drive:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook

 
(.ost) Offline Outlook Data File - is a copy (replica) of your Outlook items that is already saved on a Mail Server and don't have to be backup like a (.pst) file. 
- for Exchange Account and you want to work Offline or use the default Cached Exchange Mode (which is a copy of your Exchange Server Account Mailbox is saved on your machine in a Offline Outlook Data File and this file provides quick access to data, including when you work offline, and is sync with Exchange Server) . 
- for Outlook Connector for Windows Live Hotmail
- .ost file is automatically created and data downloaded from the mail server. 
- you can re-create this .ost file on your new computer without having to backup the .ost file. 


Location of .ost file

Windows 7 and Windows Vista    drive:\Users\user\AppData\Local\Microsoft\Outlook

Windows XP     drive:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook

 
What to do when Outlook Mailbox Quota set by Exchange Server?  
This is how we find out what is the current size of our mailbox on the mail server and how to backup the .ost files for safekeeping. 
 
Account Name <username@companyname.com> - Right click > Data File PropertiesFolder Size (button)> if you see 2 Tabs - Local Data & Server Data, it means you are working in Cached Exchange Mode


When the Exchange server do not allow you to store more than 250MB, you can create a new set of Outlook Data file with Folders for you to copy or move emails from the Exchange Account to your local hard disk drive. 

File>Info>Account Settings>Account Settings>Data Files>Add - By Default, Outlook will save under 'C:\Users\user_name\Documents\Outlook Files' path, give this file a Name, For Ex. 'My Outlook Data File Local HDD Backup.pst'. 
 
Now, every time when your mailbox is approaching its Quota Limits, just Copy or Move the entire mails from each (Exchange Account) Folder to the New Local Account Folder that you have just setup. All mails & items will reside as a backup copy in your local hard drive that still works as a normal email where you are still able to search, forward, reply and send mail as an attachment.