I don't think any shredder could erase individual mail messages.
If you're on an Outlook Exchange server, the mail is on the server not on your workstation. If you're using POP/STMP you still can't erase what was on the server and the copy on your machine is just an entry in your Outlook.pst file.
I suppose you could delete the mail from your .pst and then Erase unused space on that drive.
I am using POP mail and understand that it remains on the server, what I want to do is delete mail messages from my PC.
Suppose I move individual mail messages from Outlook and then erase them
am truly erasing it ??
AFAIK, if you move a message out of Outlook as a .msg, .rtf, .htm or .txt, you are actually making a copy of the data that is in C:\Documents and Settings\[username]\Local Settings\Application Data\Microsoft\Outlook\Outlook.pst
Erasing the copy wouldn't do anything about the deleted (but not erased) original data.