Sending Bulk Emails Hogs Exchange 2003

Hi, I wonder if anyone could shed some light on my problem.

A user sends a 6MB email to 100 recipients.

This then backs up in the message queues within exchange 2003 and takes all the bandwidth on our 1MB ASDL line bringing internet browsing to a halt.

This, if left, would be the same for at least 2 days or more which of course I could not leave so in the end had to create a new smpt protocol in exchange as I was unable to delete all the messages still queued up.

Any ideas?

Regards,

Simon