A fellow Exchange MVP recently asked if there were any free or inexpensive products to automate the merging of multiple PST files into a single PST file. There are a few applications designed to solve this problem, but unless you have lots of PST files to work through, a little manual effort using Microsoft Outlook may be all you need. (See also, "Managing PST Files in Microsoft Outlook" and "PSTs and Exchange 2010").
To merge multiple PST files into a single PST file manually with Outlook, first open the PST files within Outlook. All versions of Outlook allow you to open additional PST files. In Outlook 2007, navigate to File, Open, Outlook Data File. Then navigate to the PST file you want to open in the file system, select it, and click OK. Repeat this for multiple files. To access the PST you just mounted in Outlook, it may be helpful to change the navigation pane to Mail or even Folder View. The Folder List button is found in the bottom left of the main Outook UI. Outlook accounts are listed in alphabetical order by name within the navigation pane. You can then move Outlook content between PST files by either dragging and dropping them or by highlighting the content, right-clicking it, and selecting Move To from the context menu. Then navigate to the destination folder, and click OK. The content will be rewritten to the destination folder and removed from the source PST. If your PST is large, say more than 1GB of data, then I recommend segmenting the move into two or more smaller parts. This can get tedious if you have many PSTs or lots of content. There are third-party applications that help with this task.
The application I’ve used successfully to perform this task is called PSTMerge, developed by SysTools (http://systoolsgroup.com/). SysTools offers a feature-limited free trial of PSTMerge. The demo version merges only the first five items in each folder of any PST file. If you have many PST files to merge, then the retail version can pay for itself fairly quickly. If you just need to merge a single PST file with another, Outlook is very suitable for that task.
Throughout the versions of Outlook, there have been updates to the PST file format and schema. PSTMerge is able to open each of those and create a new Unicode.pst as the destination for the merged content. Figure 1 shows the PSTMerge interface with three PST files selected. These files can be joined, creating multiple folder hierarchies within one PST file, or they can be merged where matching folders are combined within a new PST file. You can also just have PSTMerge pull the contacts only from source PST files for merging.
My test PSTs averaged about 1.2GB and merging took about 15 minutes on my capable laptop. If you are combining many PSTs make sure they are local to the PSTMerge application and be patient. PSTMerge didn’t do a good job of updating progress bars during the merge. Figure 2 shows PSTMerge after the task has been completed.
PSTMerge does not use the Outlook.exe process; in fact, Outlook cannot have the PST files open. Finally, PSTMerge doesn’t delete the source PSTs after the merge. It leaves them there as a backup allowing the user to remove them manually. For troubleshooting, PSTMerge offers a Compare feature showing the number of items per folder for each source PST and the resulting merged PST.
PSTMerge is not a spectacular tool, but a decent performer for the task. It is useful for those who need to merge PST files fairly frequently.