Basically, try something like this...
Open Notepad, type the letter Y and then press the enter key.
Save the file with this one character in the main directory of your drive C with the name of Yes.txt.
Now, make a new file in notepad, enter this:
CD C׃/Documents and settings/<your user path to your temp folder>
Del *.* < c׃/yes.txt >null
"Save as" killtemp.bat, save this file also in the main folder of your drive C.
Right-click the above file and select "Create Shortcut"
Copy the shortcut into the Start menu "Startup" folder.
This will clear your temp folder every time you start Windows.
To clear your mails is something that you will need to track down where your mail goes and add that path in the above file you made along with a new del command line.
Don't do this if you don't fully understand what it is going to do when executed. If you specify an incorrect path, that path will be deleted and NOT to the recycle bin. Files deleted this way are GONE!.
I just saw what badge posted. His way is quite safe, my way is a bit like "What is life without the spice of danger" or "No guts, No Glory"
You decide which way to go with this.