On the Blackberry Storm you can set your preferences so that any time you send an email it is spell checked before it is sent. To turn this feature on or off, press Menu and select Options and then select Spell Check. You'll then see a bunch of options that relate to spell checking. The one you are looking for is called Spell Check Email Before Sending. Tap this to put a checkbox next to it if you want the feature on. If you want the feature off, tap so that the box is not checked.

If you make a change, press Menu and then Save to save your changes.