my email wont open even though i press the icon in the tool bar

Try restarting your Mac in Safe mode:

- Shut down your Mac

- Wait until your computer turns off and after that press the Power button

- Right after you hear the startup tone, press and hold the Shift key

- Release the Shift key when you see a grey Apple sign and the progress bar below this sign

- Once you see Desktop, start a Disk Utility scan to detect and repair file system errors (don't forget to choose your main hard drive)

- Click on Verify Disk and then, if asked to fix problems, on Repair Disk

- After this, click on Verify Disk Permissions and then on Repair Disk Permissions

- After the process is finished, shut down your Mac and turn it back on after about 30 seconds

Try rebuilding the mailbox.

Rebuild mailbox

If that doesn't work, try re-indexing the mailboxes. This can take awhile if you have a lot of mail.

Reindex messages

There is only one file in Snow Leopard.