With the current design of Recovery Solution, it is not possible to specify certain file types to be included into a partial snapshot.
It is true that according to current design, wildcards (like *.PST) cannot be used to specify certain file type to be included in a partial snapshot when there is a need to scan the entire drive for such file type and make a snapshot of those.
The attached client-side VolAgent.dll makes it possible to specify the desired file type in the Recovery Solution Agent registry. The partial snapshot settings in that case may contain any path that is needed to be backed up. The entire drive will be scanned for the specified file type to be included in the snapshot anyway.
Following text can be used as a template .reg file. The following example will tell VolAgent.dll to include all the .pst files on the C drive:
Browse to %Program Files%\Altiris\Recovery Solution Agent folder and update the VolAgent.dll with the one attached. It is recommended that you copy the new .dll over the existing one rather than moving the original .dll anywhere.
Make registry modifications as per the example given above for *.pst files.
Restart the Recovery Solution Agent Service.
The VolAgent.dll should be updated to the Data1.cab (installation package of Recovery Solution Agent). See article 24583.
There are two attachments to this article. One is for 32-bit systems, and the other one is for 64-bit systems.