Some users may migrate to another email program eventually, for instance from Microsoft Outlook to Thunderbird or an online email service like Gmail, Yahoo Mail or Hotmail. And some might want to migrate that old data to another computer, maybe one that is not running Outlook anymore, or a different version of Outlook.

That’s when things get problematic as it is not possible to just open the old Outlook inbox files on the computer then. For that, you may need to use a version of Microsoft Outlook, or a third party program like Kernel Outlook PST Viewer.

When you start the program for the first time after installation, you are asked to select a PST file from the local computer.

The software populates with all mail folders and emails, with options to read all emails that have been received or send. While it is not possible to reply to those emails directly, all the information stored in them is still available, even without access to Outlook on the system.

Other benefits of using the program include the ability to open PST files created with any existing version of Outlook, to view the contents of password protected Outlook PST files without knowing the password, and working around file corruptions.

The biggest issue that users may have is the lack of exporting tools. It is for instance not possible to extract attachments using the viewer. For that, Mailstore is the better choice as the program can make PST data available as well.

Windows users can download the latest version of Kernel Outlook PST Viewer from the developer website. The program is compatible with 32-bit and 64-bit editions of the Windows operating system. (via)

Only compressing the folders will delete that email permanently from the computer system. That’s great if you deleted an email by accident and want to recover it but bad if an unauthorized third party tries to read your emails.

Microsoft Outlook provides the means to compress a folder immediately but no option to automate the task. It will however display a popup every 100th time that Outlook got closed asking if the user wants to compress the folders.

A far better solution to force Outlook to delete deleted mails completely at every shutdown is to change a setting in the Windows Registry.

Open the Windows Registry by pressing [Windows R], typing [regedit] and hitting [enter]. Navigate to the following Registry key:

HKEY_CURRENT_USER\Software\Microsoft\Office

The next step depends on the version of Microsoft Outlook or Microsoft Office that is installed on the computer. When in doubt perform the operation for all of the following subkeys.

Find the 9.0, 10.0, 11.0 or 12.0 keys in that folder. Click in the Outlook subkey and locate the key PST. If PST is not existing create it. A full Registry path to the right location could look like this:

HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\PST\

Only the 12.0 can change in the path. If you are in the PST key right-click in the right pane and select New > DWord.

Name the Dword PSTNullFreeOnClose. Double-click it afterwards and give it the value 1 to enable it. This ensures that Microsoft Outlook will remove deleted mails completely on every exit from the computer system.

One way to sync mails between different Outlook clients would be to use a free software called Folder Share which helps you synchronize files and folders using a peer to peer network. This essentially means that you can use it to sync any data and not only the data from Outlook.

FolderShare has to be installed on all computers that you use and one account has to be created as well if you do not have one already. The software will ask you during installation if you have an account, if you select No it will automatically ask for registration. You can later on use the data from that account on the other computers as well.

You do need to install FolderShare to at least two computers to be able to sync files which should be pretty obvious. Once it is installed on two computers you click on the ‘Sync My Folders’ button on the master computer and navigate to your Outlook.pst file which can be found in C:\ Documents and Settings\ USERNAME\ Local Settings\ Application Data\ Microsoft\ Outlook if you kept the default path.

Now create a new folder for each other device that you want to sync and name it accordingly (Outlook Sync perhaps). You can select to automatically synchronize the data which is recommended. FolderShare needs to be running on at least two devices to sync the data.

Update: Foldershare has been bought by Microsoft and integrated into Windows Live products. The program is not available anymore as a standalone software to synchronize Microsoft Outlook.