M.R.
As a teacher, I'd like to offer some advice that will help you and your daughter achieve the outcome you deserve. An educator's first priority is to create and maintain a safe environment for every students.
First of all, I understand that you're upset and you have every right to be upset. You need to have a calm but assertive approach when dealing with the school. Trust me, it will get you so much farther and reach a resolution much more quickly than screaming and threatening, although it would be normal to want to go that route.
Leave a message for the teacher and the principal. Be calm yet firm when you say "This is Susie's mother, and I was notified of a bullying/harassing incident that occurred today that I find extremely troubling. I would like to meet with you as soon as possible and no later than <insert day/time> regarding how you will ensure my daughter's emotional and physical safety while attending your school."
When at the meeting, have an idea of an acceptable resolution you'd like to have happen. I know you're upset but be sure to listen to the teacher and the principal and get all the facts before making a decision. I cannot tell you how many times I have had parents call, all fired up and ready to "tell everyone" and "yank their kid out of school", only to have them calm down once they realize that the school is definitely willing to work with them to reach a solution. The school could have already done more for this boy. The boy could have some IEP that prohibits him being moved (as messed up as that sounds).
Go in with an open mind and do not leave until you think the situation is appropriately resolved. If it isn't, take it to the next level (board of education or superintendent).
There's also the chance that your daughter's teacher has not yet gotten the e-mail, especially if it was sent after the school day ended.