Hi,
We noticed that your question has went unanswered so we would like to help you out with this.
It is not currently possible to delete multiple email messages at one time on the standard Email application for the X10. However, we would recommend looking through the Android Market on your handset for third party Email applications.
Some developers have created email applications which allow this functionality.
I hope this helps you. If you need any more help please feel free to ask or send me a message.
