With the iPhone 2.0 upgrade you will find that Apple has added the ability for users to delete or move multiple message from your email inbox to a folder or delete them. In the original version of iPhone, you have to perform these basic functions with messages one at a time.
When you are in your email inbox and you press the Edit key in the upper right hand corner a blue/gray bar will appear across the bottom with two buttons: Delete and Move. Down the left side of the message summary, you'll see round buttons and if you press them it will place a check mark next to the message you wish to act upon. You may select consecutive messages or intermitten ones and then either press the Delete button to remove them or Move button to store them to another folder.