It has happened many times in my organization that some people have left in not really good terms. So when you go to check their computers you find that they normally delete their emails, sometimes you can find them in the deleted folder (lol) but sometimes they even delete them from there.
Here is a way to get them back, I would like to see how other sys admins deal with this…
Download a hex editor from google.
Open the .pst with the hexeditor and delete positions 7 and 13.(just count the letter and do space bar on top of letter at space 7 and letter at space 13.
This will corrupt the pst file. Save it.
Run SCANPST.EXE, normally located in "C:\Program Files\Common Files\System\MSMAPI\1033". It will make a backup and then it will attempt to repair the file. Once its finished, open the .pst on outlook and emails should now be there.
NOW… if you are a sysadmin and you leave the company and you don't want anyone to recover your emails, or at least make it extra harder for them… then all you need to do after deleted your email is go to (in MS Outlook) Tools > Option > Mail Set up > Data Files > Choose the .pst and click on settings > Compact Now.
Best Answer
The best way is to get control of the emails before they get deleted. I will discuss generally and point to examples for Exchange because that is the mail system I know best.
1- Get the emails off of the server and to an archive of some kind when they are created. The specific solution depends on your mail server ... GFI and Sherpa are among many available for Exchange.
2- I like IMAP idea (Robert Moir's comment to this answer). It is even better if the mail server can hold on to deleted items for a while. Exchange has a "2 level" trash bin .. one in the user mailbox, then another accessible only by admins on the server. You will have to make sure that the server has enough disk space to support all of the users mail, but disk is cheap.
3- You could also go at this using Outlook archiving, particularly if you can control the settings centrally. If you have AD this is easy to do with Group Policy. Set Outlook to archive daily to a central server location, and include that location in your nightly backups. You could also have a "rotation", moving them nightly to various locations so you have multiple versions around in the event of bad behavior.